c语言简单问题，请大家解答

#include 
#include 

int main()
{
    char a1[61]={'\0'}, a2[61]={'\0'}, b1[61]={'\0'}, b2[61]={'\0'};
    int a1_len =(int) strlen(a1);
    int a2_len = (int)strlen(a2);
    int b1_len = (int)strlen(b1);
    int b2_len = (int)strlen(b2);
    scanf_s("%s", a1, 61);
    scanf_s("%s", a2,61);
    scanf_s("%s", b1,61);
    scanf_s("%s", b2,61);
    int i;
    int flag = 0;
    for (i = 0; (i < a1_len) && (i < a2_len); i++)
    {
        if (( a1[i] >= 'A') && (a1[i] <= 'G')&&(flag==0)&&(a1[i] == a2[i]))
        {
            
            switch (a1[i] - 'A' + 1)
            {
            case 1: {printf("MON"); break; }
            case 2: {printf("TUE"); break; }
            case 3: {printf("WED"); break; }
            case 4: {printf("TUE"); break; }
            case 5: {printf("FRI"); break; }
            case 6: {printf("SAT"); break; }
            case 7: {printf("SUN"); break; }
            }
            flag++;
        }
        if ((flag == 1) &&( a1[i] == a2[i]) )
        {
            if ((a1[i] >= '0') && (a1[i] <= '9'))
            {
                printf("0%d", a1[i] - '0');
                break;
            }
            if ((a1[i] >= 'A') && (a1[i] <= 'N'))
            {
                printf("%d", a1[i] - 'A' + 10);
                break;
            }
        }
    }
    for (i = 0;( i if ((b1[i] == b2[i]) && ((b1[i] >= 'a') &&( b1[i] <= 'z') ||( b1[i] >= 'A') &&( b1[i] <= 'Z')))
        {
            if (i < 10)
                printf("0%d", i);
            else
                printf("%d", i);
            break;
        }
    }
    return 0;
}

不能正常输出，找了半天实在不知道问题在哪，请大家帮我看看

C语言代码执行是有顺序的，从上往下编译，首先你已经计算了a1-len还有a2-len，计算结果都为0，然后你虽然赋值了字符串，但并不会改变a1-len和a2-len的大小，所以a1-len和a2-len还是0，然后你for循环，肯定会崩掉的，，你应该赋值后再计算大小才对
题主如果觉得有用，望采纳，谢谢

• 帮你找了个相似的问题, 你可以看下: https://ask.csdn.net/questions/7568439
• 你还可以看下c语言参考手册中的 c语言-exp()

#include <stdio.h>
#include <string.h>
 
int main()
{
    char a1[61]={'\0'}, a2[61]={'\0'}, b1[61]={'\0'}, b2[61]={'\0'};
    scanf_s("%s", a1, 61);
    scanf_s("%s", a2,61);
    scanf_s("%s", b1,61);
    scanf_s("%s", b2,61);
    int a1_len =(int) strlen(a1);
    int a2_len = (int)strlen(a2);
    int b1_len = (int)strlen(b1);
    int b2_len = (int)strlen(b2);
    int i;
    int flag = 0;
    for (i = 0; (i < a1_len) && (i < a2_len); i++)
    {
        if (( a1[i] >= 'A') && (a1[i] <= 'G')&&(flag==0)&&(a1[i] == a2[i]))
        {
            
            switch (a1[i] - 'A' + 1)
            {
            case 1: {printf("MON"); break; }
            case 2: {printf("TUE"); break; }
            case 3: {printf("WED"); break; }
            case 4: {printf("TUE"); break; }
            case 5: {printf("FRI"); break; }
            case 6: {printf("SAT"); break; }
            case 7: {printf("SUN"); break; }
            }
            flag++;
            continue;
        }
        if ((flag == 1) &&( a1[i] == a2[i]) )
        {
            if ((a1[i] >= '0') && (a1[i] <= '9'))
            {
                printf("0%d", a1[i] - '0');
                break;
            }
            if ((a1[i] >= 'A') && (a1[i] <= 'N'))
            {
                printf("%d", a1[i] - 'A' + 10);
                break;
            }
        }
    }
    for (i = 0;( i <b1_len) &&( i < b2_len); i++)
    {
        if ((b1[i] == b2[i]) && ((b1[i] >= 'a') &&( b1[i] <= 'z') ||( b1[i] >= 'A') &&( b1[i] <= 'Z')))
        {
            if (i < 10)
                printf("0%d", i);
            else
                printf("%d", i);
            break;
        }
    }
    return 0;
}