c - 以色带为输入计算电阻值-6ren

c - 以色带为输入计算电阻值

转载作者：太空宇宙更新时间：2023-11-04 02:36:09

我试图开发一个C程序，通过输入电阻上标记的色带来计算电阻值。
忽略电阻公差。
例如

Enter the colours of the resistor’s three bands, beginning
with the band nearest the end. Type the colours in lowercase
letters only, NO CAPS
Band 1 => green
Band 2 => black
Band 3 => yellow
Resistance value: 500 000 -ohms
Do you want to decode another resistor (Y/N)?
=> Y

显示电阻值的所需格式。例如，如果电阻值为“500000-ohms”，则格式要求为
“500 000-欧姆”。必须在每3位之间加一个空格。
显示单一无效颜色。例如，如果输入“brown”、“vilet”和“red”作为电阻颜色，则程序
生成以下消息： Invalid colour: vilet仅在此处
“vilet”是唯一无效的颜色。
显示多个无效颜色。例如，如果“粉色”、“银色”和“红色”作为电阻颜色输入，则程序
应在一行中生成以下消息：
Invalid colours: pink, silver这里有两种无效颜色“粉色”和
“银色”。注意“颜色”。
现在我很难得到总阻力（#1）的格式。对于#2，如果且仅当第一个输入（波段1）无效时，程序将运行。如果第二个波段或第三个波段在第一个波段无效的情况下无效，程序将停止执行。
这是我一直在研究的代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

// resister bands
enum resistor_band_items {BLACK, BROWN, RED, ORANGE, YELLOW, GREEN, BLUE, VIOLET, GRAY, WHITE, UNKNOWN};

struct items
 {
    char *name;
    enum resistor_band_items id;
 } item_list[] = {
    {"black", BLACK},
    {"brown", BROWN},
    {"red", RED},
    {"orange", ORANGE},
    {"yellow", YELLOW},
    {"green", GREEN},
    {"blue", BLUE},
    {"violet", VIOLET},
    {"gray", GRAY},
    {"white", WHITE}
};

char answer[10], status[1] = "Y"; //answer => user input
char bands[3][10];      //string for resistor bands
//variables to hold the band values
int colour[3];
//function prototype
int inputVal (int *a, char b[3][10]);
double calResistance (int a, int b, int c);
void print_number (double number);

int main(void)
{
    int i, invalid; //counter
    double resistor_value; //total resistance value
    enum resistor_band_items mid;
    struct items *choice = NULL;

    while (strcmp(status, "Y") == 0)
    {
        //print the question to the user
        printf("Enter the colours of the resistor's three bands,\nbeginning with the band nearest to the end.\nType the coloues in lowercase letters only, NO CAPS.\n");    
        for (int j = 0; j<3; j++)
        {   
            printf("Band %d => ", j + 1);
            gets(answer);
            for (i = 0, choice = NULL; i < sizeof item_list/sizeof(struct items); ++i)
            {
                if (strcmp(answer, item_list[i].name) == 0)
                {
                    choice = item_list + i;
                    break;
                }
            }
            mid = choice ? choice ->id : UNKNOWN;
            colour[j] =  mid;
            strcpy(bands[j], answer);
        }
        invalid = inputVal (colour, bands);
        if (invalid == 0)
        {
            //calculate resistor value
            resistor_value = calResistance(colour[0], colour[1],colour[2]);
            // print resistor value to user
            printf("%.0f\n", resistor_value);
            print_number(resistor_value);
        }
        printf("Do you want to decode another resistor (Y/N)?\n");
        gets(status);
        if (strcmp(status, "Y") == 0);
        else break;
    }   
    return 0;
}
int inputVal (int *a, char b[3][10])
{
    int counter = 0, index[3];
    for (int i = 0; i < 3; ++i)
    {
        if (a[i] == 10)
        {
            index[i] = i;
            //printf("%s%s", b[i], " ");
            counter++;
        }
    }
    if (counter == 0)
    {
        return 0;
    }
    else if (counter == 1)
    {
        printf("Invalid colour: %s\n", b[index[0]]);
    }
    else if (counter == 2)
    {
        printf("Invalid colours:");
        printf(" %s", b[index[0]]);
        printf(",");
        printf(" %s\n", b[index[1]]);
    }
    else
    {
        printf("Invalid colours:");
        printf(" %s", b[index[0]]);
        printf(",");
        printf(" %s", b[index[1]]); 
        printf(",");
        printf(" %s\n", b[index[2]]);   
    }
    return 1;
}

double calResistance (int a, int b, int c)
{
    double results;
    unsigned power = 10;
    while (b >= power)
    {
        power *= 10;
    }
    results = a * power + b;
    results = results * pow(10, c);
    return results;
}

void print_number (double number)
{
    double n = number,  *x;
    int c = 0;
    int j = 1;
    while   (n != 0 && n > 1)
    {

        n /= 10.0;

        c += 1;
    }
    x = malloc (c * sizeof(double));
    printf("%d\n", c);

    for (int i = 0; i <= c; i++)
     {
        double digit = fmod (number, 10.0);
        x[i] = digit;
        number /= 10.0;
     }

     printf("Resistance value: \n\n"); 

     for (int i = c - 1; i >= 0; i--)
     {
        printf("#%d = %.0f\n",i, x[i]);
     }
    printf("\n\n\n");

    for (int i = c - 1; i >= 0; i--)
    {

        if (j == 3 || j == 7 || j == 11 || j == 15)
        {
            printf(" ");
        }
        else
        {
            printf("%.0f", x[i]);
        }
        j++;
    }
    printf(" -ohms\n");
    //free(x);
}

我已经编辑了print_number函数，所以它每3位打印一个空格。（适用于大多数组合）

void print_number (double number)
{
    double n = number,  *x;
    int c = 0;
    int j = 1;
    while   (n != 0 && n > 1)
    {

        n /= 10.0;

        c += 1;
    }
    x = malloc (c * sizeof(double));
    printf("c = %d\n", c);
    for (int i = 0; i < c; i++)
     {
        double digit = fmod (number, 10.0);
        x[i] = digit;
        number /= 10.0;
     }

     printf("Resistance value: \n"); 

     for (int i = c; i >= 0; i--)
     {
        printf("#%d = %.0f\n",i, x[i]);
     }
     printf("\n\n");
     printf("remainder of c = %d\n\n",c%3);
    if (c % 3 == 2)
    {
        for (int i = c; i >= 0; i--)
        {
            if (j == 4 || j == 7 || j == 11 || j == 15)
                {
                    printf(" ");
                    i++;
                }
                else
                {
                    printf("%.0f", x[i]);
                }
            j++;
        }
        printf(" -ohms\n"); 
    }
    else
    {
        for (int i = c - 1 ; i >= 0; i--)
        {
            //printf("%.0f", x[i]);

            if (c % 3 == 0)
            {
                if (j == 4 || j == 8 || j == 12 || j == 16)
                {
                    printf(" ");
                    i++;
                }
                else
                {
                    printf("%.0f", x[i]);
                }
            }
            else if (c % 3 == 1)
            {
                if (j == 2 || j == 6 || j == 10 || j == 14)
                {
                    printf(" ");
                    i++;
                }
                else
                {
                    printf("%.0f", x[i]);
                }
            }   
            j++;
        }
        printf(" -ohms\n");
        //free(x);      
    }
}

第2版
这里是修改后的答案代码。
我不使用 argc和 argv的原因是客户端有一个需要遵循的受限格式（这让我很生气！）
代码如下：

    //importing required header files
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

// resister bands
enum resistor_band_items {BLACK, BROWN, RED, ORANGE, YELLOW, GREEN,
                                 BLUE, VIOLET, GRAY, WHITE, UNKNOWN};

//constants for min/max colour arguments and max colour char
enum {MINC = 3, MAXC = 4, MAXCC = 8};
struct items
 {
    char *name;
    enum resistor_band_items id;
 } item_list[] = {
    {"black", BLACK},
    {"brown", BROWN},
    {"red", RED},
    {"orange", ORANGE},
    {"yellow", YELLOW},
    {"green", GREEN},
    {"blue", BLUE},
    {"violet", VIOLET},
    {"gray", GRAY},
    {"white", WHITE}
};
//resistor multiplier values
int multiplier[] = {1, 10, 100, 1000, 10000, 100000, 1000000, 10000000};
char answer[3][10]; // User input
int colour_val[3]; //stores the band value

#define nItems (sizeof item_list/sizeof *item_list)
//function prototyps
int srchItems (char *ccode); //a search for index values
char *strcpy2lower (char *dest, char *src); //converts to lower case
int scmp (char *a, char *b); //simple string comarison
char *sepnumber (char *s, long val);
int invalid (char answer[3][10]);
//main function
int main(int argc, char const *argv[])
{
    int i; // counter 
    char status = 'Y';// Keeps the program running when user inputs 'Y'
    long resistor_value = 0; //Total resistance
    int r, err, mult; //holds the significant figure, Error, Multiplier
    char resistor_value_string[20] = "";//formatted output
    while (status == 'Y') //The program runs under this
    {
        //print the question to the user
        printf("Enter the colours of the resistor's three bands,\nbeginning with the band nearest to the end.\nType the coloues in lowercase letters only, NO CAPS.\n");
        for (i = 0; i < MINC; ++i)
        {
            printf("Band %d => ", i + 1); // print headers for each band
            scanf(" %s", &answer[i]);  // get the user input
        }
        for (i = 0; i < MINC - 1; ++i) //converts colours into index
        {
            if ((r = srchItems (answer[i])) > -1)
            {
                // from significant figure
                resistor_value = (resistor_value * 10) + r;
            }
            else
            {
                invalid(answer);
                err = 2; 

            }
        }
        if (err > 1)
        {
            printf("Do you want to decode anothe resistor (Y/N)?\n");
            scanf (" %c", &status);
            if (status == 'Y');
            else break; 
        }
        else
        {
            mult = srchItems (answer[i]);       // get multiplier index
            resistor_value *= multiplier[mult]; // Calculate final value

            sepnumber (resistor_value_string, resistor_value);
            printf("Resistor value: ");
            /*for (int i = 0; i < (strlen(resistor_value_string) ); ++i)
            {
                printf("%c", resistor_value_string[i]);
            }
            */
            puts (resistor_value_string);   
            //printf(" -ohm\n");
            //memset (resistor_value_string, 0, 50);
            printf("Do you want to decode anothe resistor (Y/N)?\n");
            scanf (" %c", &status);
            if (status == 'Y');
            else break;
            /*Debug 
            for (int i = 0; i < MINC; ++i)
            {
                printf("item_list[%d] = %s\n", i, answer[i]);
            }
            printf("Total resistance = %ld\n", resistor_value);
            //end of debug */
        }
    }
    return 0;
}

int srchItems (char *ccode)
{
    int i;
    char lccode [MAXCC] = "";
    strcpy2lower (lccode, ccode); // converts everything to lower case
    for (int i = 0; i < (int)nItems; ++i) 
        if (*lccode == *(item_list[i].name))
            if (!scmp(item_list[i].name, lccode))
                return i;
    return -1;
}

char *strcpy2lower (char *dest, char *src)
{
    if (!src || !dest) return NULL;
    char *d = dest;
    for (; *src; src++, d++)
        if ('A' <= *src && *src <= 'Z')
            *d = *src | (1 << 5);
        else
            *d = *src;
    *d = 0;
    return dest;
}

int scmp (char *a, char *b)
{
    if (!a && !b) return 0;
    if ( a && !b) return 1;
    if (!a &&  b) return -1;

    for (; *a && *b && *a == *b; a++, b++) {}

    return *a - *b;
}


/** separate long value every 3rd char into 's' */
char *sepnumber (char *s, long val)
{
    char numstr[3 * MAXCC] = "";
    char *p = numstr;
    size_t idx = 0, len = 0;

    sprintf (numstr, "%ld", val);
    for (; *p; p++) {}
    len = p - numstr;
    p = s + 3 * MAXCC - 2;

    while (len--) {
        if (idx++ == 3) {
            idx = 1;
            *p-- = ' ';
        }
        *p = numstr[len];
        if (len) p--;
    }
    for (idx = 0; *p; p++, idx++) s[idx] = *p; /* copy to s */
    s[idx] = *p;    /* nul-terminate */
    return s;
}

int invalid (char answer[3][10])
{
    int r, counter = 0, incorrect[3], i;

    for (i = 0; i < MINC; ++i)
    {
        if ((r = srchItems (answer[i])) == -1)
        {
            incorrect[i] = r;
            counter++;
        }
    }
    if (counter == 1)
    {
        printf("%s","Invalid colour: " );
        printf("%s ", answer[i]);
        printf("\n");
    }
    i = 0;
}

这个转速在第一个回路中运行良好，但在第二个回路中计算错误的电阻值。
它会很难打印出无效的条目！
输入无效颜色后，程序将不计算任何电阻值。
输出示例：

$ ./RQ1.exe
Enter the colours of the resistor's three bands,
beginning with the band nearest to the end.
Type the coloues in lowercase letters only, NO CAPS.
Band 1 => red
Band 2 => orange
Band 3 => green
Resistor value: 2 300 000
Do you want to decode anothe resistor (Y/N)?
Y
Enter the colours of the resistor's three bands,
beginning with the band nearest to the end.
Type the coloues in lowercase letters only, NO CAPS.
Band 1 => green
Band 2 => black
Band 3 => yellow
Resistor value: -2 101 970 656
Do you want to decode anothe resistor (Y/N)?
Y
Enter the colours of the resistor's three bands,
beginning with the band nearest to the end.
Type the coloues in lowercase letters only, NO CAPS.
Band 1 => read
Band 2 => gren
Band 3 => blu
Do you want to decode anothe resistor (Y/N)?
Y
Enter the colours of the resistor's three bands,
beginning with the band nearest to the end.
Type the coloues in lowercase letters only, NO CAPS.
Band 1 => red
Band 2 => orange
Band 3 => green
Do you want to decode anothe resistor (Y/N)?
N

最终版本，
我想是这样的：）除了显示无效输入仍然有问题。
因为帮了这么多忙，真是个大坦克。

#include <stdio.h>
#include <string.h>

#define nItems (sizeof item_list/sizeof *item_list)

char status = 'Y'; 
//
enum {MINC = 3, MAXCC = 10};
// resister bands
enum resistor_band_items {BLACK, BROWN, RED, ORANGE, YELLOW, GREEN,
                                 BLUE, VIOLET, GRAY, WHITE, UNKNOWN};
struct items
 {
    char *name;
    enum resistor_band_items id;
 } item_list[] = {
    {"black", BLACK},
    {"brown", BROWN},
    {"red", RED},
    {"orange", ORANGE},
    {"yellow", YELLOW},
    {"green", GREEN},
    {"blue", BLUE},
    {"violet", VIOLET},
    {"gray", GRAY},
    {"white", WHITE}
};
unsigned int multiplier[] = {1, 10, 100, 1000, 10000, 100000, 1000000,
     10000000, 100000000, 1000000000};

int srchItems (char *ccode); //a search for index values
char *strcpy2lower (char *dest, char *src); //converts to lower case
int scmp (char *a, char *b); //simple string comarison
char *sepnumber (char *s, long val); //puts space every 3rd digit

int main(void)
{
    int i, error = 0, mult;
    char input[MINC][MAXCC]; //user input
    char invalid[MINC][MAXCC]; // invalid enteries
    int colour_val[MINC]; //stores the band value
    long total_resistance = 0; 
    char resistor_value_string[20] = "";//formatted output
    do
    {
    //prompt user 
    printf("%s\n%s\n%s\n",
        "Enter the colours of the resistor's three bands,",
        "beginning with the band nearest to the end.",
        "Type the colours in lowercase letters only, NO CAPS.");

    for (i = 0; i < MINC; ++i)
    {
        printf("Band %d => ", i + 1); // print headers for each band
        scanf(" %s", &input[i]);  // get the user input
        // converts user input to index of colours
        colour_val[i] = srchItems(input[i]); 
    }       
    for (i = 0; i < MINC; ++i)
    {
        if (colour_val[i] == -1)
        {
            strcpy(invalid[i], input[i]);
            error++;
        }
    }
    if (error > 0)
    {
        if (error == 1)
        {
            printf("Invalid colour: %s\n", invalid[0]);
        }
        else if (error == 2)
        {
            printf("Invalid colours: %s, %s\n", invalid[0], invalid[1]);
        }
        else 
        {
            printf("Invalid colours: %s, %s, %s\n",
             invalid[0], invalid[1], invalid[2]);
        }
    }
    else
    {
        //
        for (i = 0; i < MINC - 1; ++i)
        {
            total_resistance = (total_resistance * 10) + colour_val[i];
        }
        mult = colour_val[2];
        total_resistance *= multiplier[mult];
        sepnumber (resistor_value_string, total_resistance);

        printf("Resistance value: %s -Ohms\n", resistor_value_string);
//debug
        for (i = 0; i < MINC; ++i)
        {
            //printf("Input ==> %s\t", input[i]);
            //printf("index ==> %d\n", colour_val[i]);
        }
//end debug
    }
    error = 0;
    total_resistance = 0;
    for (i = 0; i < MINC; ++i)
    {
        colour_val[i] = 0;
    }
    //ask user if they want to continue
    printf("Do you want to decode another resistor?\n");
    scanf(" %c", &status);


    if (status == 'Y');
    else break;

    } while (status == 'Y');



    return 0;
}

int srchItems (char *ccode)
{
    int i;
    char lccode [MAXCC] = "";
    strcpy2lower (lccode, ccode); // converts everything to lower case
    for (int i = 0; i < (int)nItems; ++i) 
        if (*lccode == *(item_list[i].name))
            if (!scmp(item_list[i].name, lccode))
                return i;
    return -1;
}

char *strcpy2lower (char *dest, char *src)
{
    if (!src || !dest) return NULL;
    char *d = dest;
    for (; *src; src++, d++)
        if ('A' <= *src && *src <= 'Z')
            *d = *src | (1 << 5);
        else
            *d = *src;
    *d = 0;
    return dest;
}

int scmp (char *a, char *b)
{
    if (!a && !b) return 0;
    if ( a && !b) return 1;
    if (!a &&  b) return -1;

    for (; *a && *b && *a == *b; a++, b++) {}

    return *a - *b;
}

/** separate long value every 3rd char into 's' */
char *sepnumber (char *s, long val)
{
    char numstr[3 * MAXCC] = "";
    char *p = numstr;
    size_t idx = 0, len = 0;

    sprintf (numstr, "%ld", val);
    for (; *p; p++) {}
    len = p - numstr;
//printf("%d\n", len);
    p = s + 3 * MAXCC - 2;

    while (len--) {
        if (idx++ == 3) {
            idx = 1;
            *p-- = ' ';
        }
        *p = numstr[len];
        if (len) p--;
    }
    for (idx = 0; *p; p++, idx++) s[idx] = *p; /* copy to s */
    s[idx] = *p;    /* nul-terminate */
    return s;
}

输出示例

$ ./Q1_token.exe
Enter the colours of the resistor's three bands,
beginning with the band nearest to the end.
Type the colours in lowercase letters only, NO CAPS.
Band 1 => green
Band 2 => black
Band 3 => yellow
Resistance value: 500 000 -Ohms
Do you want to decode another resistor?
Y
Enter the colours of the resistor's three bands,
beginning with the band nearest to the end.
Type the colours in lowercase letters only, NO CAPS.
Band 1 => red
Band 2 => orange
Band 3 => green
Resistance value: 2 300 000 -Ohms
Do you want to decode another resistor?
Y
Enter the colours of the resistor's three bands,
beginning with the band nearest to the end.
Type the coloues in lowercase letters only, NO CAPS.
Band 1 => pink
Band 2 => silver
Band 3 => red
Invalid colours: pink, silver
Do you want to decode another resistor?
Y
Enter the colours of the resistor's three bands,
beginning with the band nearest to the end.
Type the colours in lowercase letters only, NO CAPS.
Band 1 => vilot
Band 2 => brown
Band 3 => read
Invalid colours: vilot, silver
Do you want to decode another resistor?
N

最佳答案

确定电阻值有效数字的代码比需要的要复杂得多。由于您声明了structitem_list的全局数组，所以要形成有效数字，只需使用item_list作为查找表来查找输入的色带的索引。对于随后的每种颜色（第二种颜色[第三种颜色为5波段]），只需在添加索引之前将当前电阻值乘以10。
例如，使用索引变量item_list和电阻值r（包括检查是否存在无效颜色），代码可以减少为：

int multiplier[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000 };
...
    int err = 0, i, mult, r;
    long rval = 0;

    printf ("\ncolor bands determining significant figures:\n\n");
    for (i = 1; i < argc - 1; i++) { /* convert colors to index */
        if ((r = srchitems (argv[i])) != -1) {
            rval = rval * 10 + r;    /* form significant figure */
            prnitem (r);
        }
        else {
            fprintf (stderr, "error: invalid color '%s'\n", argv[i]);
            err = 1;
        }
    }
    if (err) return 1;
    mult = srchitems (argv[i]);     /* get multiplier index  */
    rval *= multiplier[mult];       /* calculare final value */
    printf ("\nmultiplier:\n\n");
    prnitem (mult);
    printf ("\nresistor value : %ld -ohms\n\n", rval);

    return 0;

上面的 rval函数只返回给定颜色的 srchitems中的索引（作为程序的参数输入，例如 item_list， argv[1]，…），您可以编写一个简单的 argv[2]，在执行查找之前将所有输入转换为小写：

/** search item_list for color code 'ccode', return index
 *  returns array index on success, -1 otherwise.
 */
int srchitems (char *ccode)
{
    int i;
    char lccode[MAXCC] = "";       /* array to hold lowercase color */

    strcpy2lower (lccode, ccode);  /* convert string to lowercase */

    for (i = 0; i < (int)nitems; i++)    /* lookup index */
        if (*lccode == *(item_list[i].name))
            if (!scmp (item_list[i].name, lccode))
                return i;

    return -1;   /* return -1 on error */
}

如果你把剩下的拼图拼凑在一起，你可以做类似于下面的事情。我把它留给你根据需要格式化输出。您可以将简单的字符串比较函数 srchitems替换为 scmp（包括 strcmp）如果有任何问题，请告诉我。

#include <stdio.h>

/* resister bands */
enum resistor_band_items { BLACK, BROWN, RED, ORANGE, YELLOW, GREEN, 
                        BLUE, VIOLET, GRAY, WHITE, UNKNOWN };
/* constants for min/max color arguments and max color chars */
enum { MINC = 3, MAXC = 4, MAXCC = 8 };

struct items    /* could be simple array of strings */
{
    char *name;
    enum resistor_band_items id;
} item_list[] = {
    {"black", BLACK},
    {"brown", BROWN},
    {"red", RED},
    {"orange", ORANGE},
    {"yellow", YELLOW},
    {"green", GREEN},
    {"blue", BLUE},
    {"violet", VIOLET},
    {"gray", GRAY},
    {"white", WHITE}
};
/* resistor multiplier values */
int multiplier[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000 };

#define nitems (sizeof item_list/sizeof *item_list)

int srchitems (char *ccode);
char *strcpy2lower (char *dest, char *src);
int scmp (char *a, char *b);
void prnitem (int i);

int main (int argc, char **argv) {

    if (argc < MAXC || MAXC + 1 < argc) { /* check 3 or 4 arguments */
        fprintf (stderr, "error: invalid input, usage: %s c1 c2 c3 [c4]\n"
                         "usage: enter color codes for 4 or 5-band resistor\n"
                         "       (tolerance ignored, enter 4 colors max)\n",
                        argv[0]);
        return 1;
    }

    int err = 0, i, mult, r;
    long rval = 0;

    printf ("\ncolor bands determining significant figures:\n\n");
    for (i = 1; i < argc - 1; i++) { /* convert colors to index */
        if ((r = srchitems (argv[i])) != -1) {
            rval = rval * 10 + r;    /* form significant figure */
            prnitem (r);
        }
        else {
            fprintf (stderr, "error: invalid color '%s'\n", argv[i]);
            err = 1;
        }
    }
    if (err) return 1;
    mult = srchitems (argv[i]);     /* get multiplier index  */
    rval *= multiplier[mult];       /* calculare final value */
    printf ("\nmultiplier:\n\n");
    prnitem (mult);
    printf ("\nresistor value : %ld -ohms\n\n", rval);

    return 0;
}

/** search item_list for color code 'ccode', return index
 *  returns array index on success, -1 otherwise.
 */
int srchitems (char *ccode)
{
    int i;
    char lccode[MAXCC] = "";

    strcpy2lower (lccode, ccode);

    for (i = 0; i < (int)nitems; i++)
        if (*lccode == *(item_list[i].name))
            if (!scmp (item_list[i].name, lccode))
                return i;

    return -1;
}

/** copy and convert string to lowercase.
 *  returns copy of string with all chars converted to lowercase.
 *  ('dest' must be of sufficient size of hold 'src')
 */
char *strcpy2lower (char *dest, char *src)
{
    if (!src || !dest) return NULL;

    char *d = dest;

    for (; *src; src++, d++)
        if ('A' <= *src && *src <= 'Z')
            *d = *src | (1 << 5);
        else
            *d = *src;

    *d = 0;

    return dest;
}

/** simple string comparison (like strcmp) */
int scmp (char *a, char *b)
{
    if (!a && !b) return 0;
    if ( a && !b) return 1;
    if (!a &&  b) return -1;

    for (; *a && *b && *a == *b; a++, b++) {}

    return *a - *b;
}

void prnitem (int i)
{
    printf (" item_list[%d]  name: %-6s  id: %d\n", 
            i, item_list[i].name, item_list[i].id);
}

示例使用/输出
有效电阻颜色（大写或小写字符都可以）

$ ./bin/resistor green blue yellow

color bands determining significant figures:

 item_list[5]  name: green   id: 5
 item_list[6]  name: blue    id: 6

multiplier:

 item_list[4]  name: yellow  id: 4

resistor value : 560000 -ohms


$ ./bin/resistor Red Orange Violet Black

color bands determining significant figures:

 item_list[2]  name: red     id: 2
 item_list[3]  name: orange  id: 3
 item_list[7]  name: violet  id: 7

multiplier:

 item_list[0]  name: black   id: 0

resistor value : 237 -ohms

无效颜色会产生个别错误：

$ ./bin/resistor pink silver green

color bands determining significant figures:

error: invalid color 'pink'
error: invalid color 'silver'

每隔3个字符拆分数字
为什么不直接将 string.h转换为字符串（不带小数点），然后从末尾将字符复制到新字符串并每3个字符添加一个 number呢？这不是一个相当复杂的方法，您依赖于数值计算来测试/分离您的数字？这让事情变得简单多了。（即使您使用 space是出于一些前所未闻的原因——假设您最终会合并容忍度），但这种方法确实没有什么区别。请尝试以下操作：

void print_number (double number)
{
    char numstr[3 * MAXCC] = "", sepstr[3 * MAXCC] = "";
    char *p = NULL;
    size_t idx = 0, len = 0;

    sprintf (numstr, "%.0lf", number);  /* write double to string */
    len = strlen (numstr);              /* get length */
    p = sepstr + 3 * MAXCC - 2;         /* set p at last char in sepstr */

    while (len--) {         /* for each char in numstr */
        if (idx++ == 3) {   /* if 3 characters copied  */
            idx = 1;        /* reset index */
            *p-- = ' ';     /* write a space in sepstr */
        }
        *p = numstr[len];   /* write char in sepstr    */
        if (len) p--;       /* decrement p if not at 0 */
    }

    printf ("p : '%s'\n", p);  /* print the separate value */
}

注意，如果出于格式化原因想让数组返回到 double中，您可以简单地将字符数组传递给 print_number并将 p复制到数组中（在这种情况下，您甚至可以更改 main以返回 print_number。）让我知道它是否有效。如果你不能那样做，那么我将研究你的数字逻辑，但那需要阿司匹林，而且可能在早上 char *
示例 :)输出

           5 => '5'
          55 => '55'
         555 => '555'
        5555 => '5 555'
       55555 => '55 555'
      555555 => '555 555'
     5555555 => '5 555 555'
    55555555 => '55 555 555'
   555555555 => '555 555 555'

实际实施示例
下面是我在代码中实现它的方法。实际上，您只需将 print_number声明/初始化移到 sepstr中，然后将其作为数组传递给您的 main（下面的my print_number）。

char *sepnumber (char *s, long val);
...
    long rval = 0;
    char rstr[3 * MAXCC] = "";
    ...
    printf ("\nresistor value : %s -ohms\n\n", sepnumber (rstr, rval));

    return 0;
}
...
/** separate long value every 3rd char into 's' */
char *sepnumber (char *s, long val)
{
    char numstr[3 * MAXCC] = "";
    char *p = numstr;
    size_t idx = 0, len = 0;

    sprintf (numstr, "%ld", val);
    for (; *p; p++) {}
    len = p - numstr;
    p = s + 3 * MAXCC - 2;

    while (len--) {
        if (idx++ == 3) {
            idx = 1;
            *p-- = ' ';
        }
        *p = numstr[len];
        if (len) p--;
    }
    for (idx = 0; *p; p++, idx++) s[idx] = *p; /* copy to s */
    s[idx] = *p;    /* nul-terminate */

    return s;
}

示例/输出

$ ./bin/resistor green blue yellow

color bands determining significant figures:

 item_list[5]  name: green   id: 5
 item_list[6]  name: blue    id: 6

multiplier:

 item_list[4]  name: yellow  id: 4

resistor value : 560 000 -ohms


$ ./bin/resistor Red Orange Violet Brown

color bands determining significant figures:

 item_list[2]  name: red     id: 2
 item_list[3]  name: orange  id: 3
 item_list[7]  name: violet  id: 7

multiplier:

 item_list[1]  name: brown   id: 1

resistor value : 2 370 -ohms

循环输入时重新初始化值
根据您对问题的描述，我强烈怀疑您遇到的问题是由于在每个循环的末尾（或某些类似的值）没有重置/重新初始化 sepnumber（您的 rval = 0;）。始终检查哪些值可能是累加值等，并记住在每个循环开始时重置这些值。在大多数情况下处理此问题的另一种方法是在循环范围内声明变量，以便在每次迭代时自动重新初始化它们。
使用block scope作为循环，您的 resistor_value应该类似于以下内容：

int main (void) {

    for (;;) {                      /* loop for input */
        int err = 0, i, mult, r;    /* variables have block scope only */
        long rval = 0;
        char ccode[MAXCC] = "", rstr[3 * MAXCC] = "";

        printf ("\nEnter the colours of the resistor's three bands,\n"
                "beginning with the band nearest to the end.\n");
        for (i = 0; i < MINC; i++) { /* convert colors to index */
            printf ("Band %d => ", i + 1);
            if (scanf (" %7s", ccode) != 1) {
                fprintf (stderr, "error: invalid input or EOF.\n");
                return 1;
            }
            if ((r = srchitems (ccode)) != -1) {
                if (i < 2) {
                    rval = rval * 10 + r;    /* form significant figure */
                }
                else {
                    mult = srchitems (ccode);  /* get multiplier index  */
                    rval *= multiplier[mult];  /* calculare final value */
                }
            }
            else {
                fprintf (stderr, "error: invalid color '%s'\n", ccode);
                err = 1;
            }
        }
        if (err) return 1;
        printf ("Resistor value : %s -ohms\n", sepnumber (rstr, rval));
        printf ("\nDo you want to decode another resistor (y/n)? ");
        if (scanf (" %7s", ccode) != 1) {
            fprintf (stderr, "error: invalid input or EOF.\n");
            return 1;
        }
        if (*ccode != 'y' && *ccode != 'Y') break;
    }

    return 0;
}

示例使用/输出

$ ./bin/resistor2

Enter the colours of the resistor's three bands,
beginning with the band nearest to the end.
Band 1 => green
Band 2 => blue
Band 3 => yellow
Resistor value : 560 000 -ohms

Do you want to decode another resistor (y/n)? y

Enter the colours of the resistor's three bands,
beginning with the band nearest to the end.
Band 1 => red
Band 2 => orange
Band 3 => orange
Resistor value : 23 000 -ohms

Do you want to decode another resistor (y/n)? n

我想你可以用这个暗示找到你的错误。

关于c - 以色带为输入计算电阻值，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/37019527/

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c - 以色带为输入计算电阻值