c - 为什么程序不执行切换？

Question

这是一个简单的密码。我不太明白为什么 switch 语句不会执行。 switch 语句之前的所有内容都有效。如果您能简要解释如何解决此问题，那就太好了。我最近开始用 C 编码，所以如果这是一个愚蠢的问题，我很抱歉!预先感谢您!

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

int main()
{

    char letter;    
    char word[100];

    int i;
    int j; 
    int x;

    int shift;
    int stringLength;

    printf("Enter d to DECRYPT.\n");
    printf("Enter e to ENCRYPT.\n");

    scanf("%c", & letter);

    if(letter == 'd' || letter == 'D') // d = 0, e = 1
    {
        x = 0;
    }
    else if(letter == 'e' || letter == 'E')
    {
        x = 1;
    }
    else
    {
        printf("The letter you entered was neither d or e!\n");
        return 0;
    }

    printf("\nEnter the number of shifts:\n");
    scanf("%d", &shift);

    printf("\nEnter the word or phrase you would like to Encrypt or Decrpyt\n");
    scanf("%s", word);
    //printf("\nThe word you entered was:\n%s\n", word);

    stringLength = strlen(word);
    //printf("\nThe size of the string is: %i\n", stringLength);

    switch(x)
    {
        case 0:     // decrypt

            for(i = 0; (i < 100 && word[i] != '\0'); i++)
                word[i] = word[i] - shift;

            break;

            /*
             *    while(i < stringLength)
             *    {
             *        word[i] = word[i] - shift;
             *        i++;
             *        
             *        printf("The Decrypted word is: %s\n", word);
             */
            //break;

        case 1: // encrypt

            for(i = 0; (i < 100 && word[i] != '\0'); i++)
                word[i] = word[i] + shift;

            break;


            /*
             * while( i < stringLength)
             * {
             *    word[i] = word[i] + shift;
             *    i++;
             * 
             *    printf("The Encrypted word is: %s\n", word);
             */
    }

    return 0;
}

Answer 1

您的switch正在执行，但每个case的正文中有太多注释掉的部分。

使用 fgets 而不是 scanf 作为短语，因为 scanf 只会获取第一个单词。

旁注:我会使用 #if 0 和 #endif 而不是 /* 和 */ 注释掉代码块。

请注意，虽然您可以混合使用 scanf 和 fgets，但我已重新编码为仅使用 fgets 和strtol。

这是清理后的工作代码[请原谅无偿的清理方式]:

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

char word[100];

void
get(void)
{

    fgets(word,sizeof(word),stdin);
    char *cp = strchr(word,'\n');
    if (cp != NULL)
        *cp = 0;

}

int
main()
{

    char letter;

    int i;
    int j;
    int x;

    int shift;
    int stringLength;

    printf("Enter d to DECRYPT.\n");
    printf("Enter e to ENCRYPT.\n");

    get();
    letter = word[0];

    if (letter == 'd' || letter == 'D') // d = 0, e = 1
    {
        x = 0;
    }
    else if (letter == 'e' || letter == 'E') {
        x = 1;
    }
    else {
        printf("The letter you entered was neither d or e!\n");
        return 0;
    }

    printf("\nEnter the number of shifts:\n");
    get();
    shift = strtol(word,NULL,10);

    printf("\nEnter the word or phrase you would like to Encrypt or Decrpyt\n");
#if 0
    scanf("%s", word);
#else
    get();
#endif
    printf("\nThe word you entered was:\n%s\n", word);

    stringLength = strlen(word);
    printf("\nThe size of the string is: %i\n", stringLength);

    printf("x=%d\n", x);
    switch (x) {
    case 0:                         // decrypt
        printf("decrypt case\n");

        for (i = 0; (i < 100 && word[i] != '\0'); i++)
            word[i] = word[i] - shift;

#if 0
        while (i < stringLength) {
            word[i] = word[i] - shift;
            i++;
        }

#endif
        printf("The Decrypted word is: %s\n", word);
        break;

    case 1:                         // encrypt
        printf("encrypt case\n");
        for (i = 0; (i < 100 && word[i] != '\0'); i++)
            word[i] = word[i] + shift;

#if 0
        while (i < stringLength) {
            word[i] = word[i] + shift;
            i++;
        }
#endif

        printf("The Encrypted word is: %s\n", word);
        break;
    }

    return 0;
}