C语言字符串逆序的方法

1. 使用两个指针

#include <cstdio>
#include <cstring>

char *reverse_str(char *str)
{
    if (str == NULL || *str == '') {
        return NULL;
    }
    char* start = str;

    char* end = str;
    while (*end != '') end++;   
    end--;
 
    while (start < end) {
        char t = *start;
        *start++ = *end;
        *end-- = t ;
    }

    return str;
}

int main(int argc, char *argv[])
{
    if (argc != 2) {
        printf("need on param !
");
        return 0;
    }
    printf("%s
", argv[1]);
    printf("%s
", reverse_str(argv[1]));
    return 0;
}

2. 递归函数

void reverse_str(char* s, int left, int right)
{
    if (left >= right) {
        return;
    }
 
    char t = s[left];
    s[left] = s[right];
    s[right] = t;
 
    reverse_str(s, left + 1, right - 1);
}

int main(int argc, char *argv[])
{
    if (argc != 2) {
        printf("need on param !
");
        return 0;
    }
    printf("%s
", argv[1]);
    reverse_str(argv[1], 0, strlen(argv[1]) - 1);
    printf("%s
", argv[1]);
    return 0;
}