c++ - 这段代码有什么问题吗？如果它是字母，我无法测试名为 number 的变量

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已关闭 7 年前。

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有人可以帮助我理解我的代码有什么问题吗？一切都很顺利，直到 p 指针在分配的内存上带来一个字母而不是数字。

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

int main() {
    int key;
    int c = 0;
    int number;
    int coins;
    int coins2;
    char answear;
    int n;
    int* p;
    FILE* fp;
    fp = fopen("D://coins.txt", "r");
    PAR2: coins = 100;
    if (!fp) // daca fp nu exista;
    {
        printf("No previous data!.\n");
    }
    if (!feof(fp)) // the condition to be read line by line from the txt file.
    {
        printf("Taking values:\n");
        fscanf(fp, "%d", & c); //reading values from the savegame.
        coins = c; //getting coins from the savegame.
    }
    fclose(fp);
    for (n = 1; n > 0;) //infinite loop
    {
        if (coins <= 0) //if running out of coins
        {
            PAR4: printf("Sorry but you have no dollars left. Try again Y/N?\n");
            PAR3: answear = getch();
            switch (answear) //testing answear
            {
            case 'Y':
                {
                    goto PAR2; //give 100
                }
            case 'y':
                {
                    goto PAR2; //give 100
                }
            case 'N':
                {
                    exit(1);
                }
            case 'n':
                {
                    exit(1);
                }
            default: //if the answear if undifined
                {
                    printf("Not an option. Answear only with Y/N!\n");
                    goto PAR3;
                }
            }
        }
        PAR1: printf("You have: %d$\n", coins);
        printf("\nEnter your number! WARNING: it must be between 1 and 5 only.\n");
        p = (int*)malloc(sizeof(int)); //memory for number variable
        scanf("%d", p); //take the number
        if (*p > 0 && *p < 6) //I need the number to be between 1 and 5
        {
            printf("Your number is: %d\n", number);
            showing the chosen number
            key = (rand() % 5) + 1; //generating a random key
            printf("The extracted number is: %d\n", key);
            if (key == number)
                if the key is guessed {
                printf("Congratulations! You have won 10$.\n");
                coins2 = coins + 10;
            } else {
                printf("You are not so lucky this time!\n");
                coins2 = coins - 10;
            }
            coins = coins2;
            printf("Rotate again? Y/N!\n");
            play again ?
                PAR5 : answear = getch();
            switch (answear) //test the answear
            {
            case 'Y':
                {
                    system("cls"); //clear screen
                    goto PAR4; //going to the starting of the loop
                }
            case 'y':
                {
                    system("cls");
                    clear screen
                    goto PAR4; //going to the starting of the loop
                }
            case 'N':
                {
                    fp = fopen("D://coins.txt", "w");
                    save the coins
                    fprintf(fp, "%d", coins);
                    fclose(fp);
                    exit(1);
                }
            case 'n':
                {
                    fp = fopen("D://coins.txt", "w"); //save the coins
                    fprintf(fp, "%d", coins);
                    fclose(fp);
                    exit(1);
                }
            default:
                {
                    printf("Not an option. Answear only with Y/N!\n");
                    goto PAR5;
                }
            }
        } else
            printf("Wrong number:\n");
        /*
    Message if a letter or symbol has been entered (this message is shown over and over again, and I don't know why...)
    even if it's infinite loop, the loop it should reset so it should again pass the statements above, but it doesn't. 
    */
        free(p); // free the number.
    }
    getch();
    return 0;
}

Answer 1

您无法通过测试 feof(fp) 来检查是否可以从文件中读取数据。您必须尝试读取并检查读取 API 的返回值:getchar() 将在文件末尾返回 EOF，fgets() > 将返回NULL。 scanf() 将返回 EOF。 feof() 函数只能在读取操作到达文件末尾之后使用。

除此之外，您的代码无法编译，它充其量是伪代码，最坏的情况是翻译得很糟糕的基本意大利面条代码。

不要以这种方式使用标签和 goto，用循环和测试来构建代码，并且可能将其中一些拆分为单独的函数。