C语言 strcmp返回值的玄学问题

Question

发现一个 strcmp 很离谱的问题 求解答！

运行成功的代码：

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


int main() {
    char weekdays[ ][10]={"Sunday", "Monday", "Tuesday", "Wednesday",
     "Thursday", "Friday", "Saturday"};
    char temp[10];
    int i, j; 
    int n = 7;
    printf("%d\n\n", strcmp(weekdays[2], weekdays[1]));
    
    for (i = 0; i < n - 1; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            if (strcmp(weekdays[j], weekdays[j + 1]) > 0) {
                strcpy(temp, weekdays[j]);
                strcpy(weekdays[j], weekdays[j + 1]);
                strcpy(weekdays[j + 1], temp);
            }
        }
    }
    for (i = 0; i < n; i++) {
        printf("%s", weekdays[i]);
    }
    return 0;
}

但是，如果将第15行的 if (strcmp(weekdays[j], weekdays[j + 1]) > 0) 改成 if (strcmp(weekdays[j], weekdays[j + 1]))
就排序错误了

Answer 1

if语句用来判断真假。if(a>0)，则要求a必须大于0才成立，而if(a)则只要a不等于0就成立，你改了之后，只要两字符串不相等，strcmp()就不会返回0，所以无论哪个字符串大，if条件都成立，所以你的程序会排序错误。望采纳谢谢！