Reverse a String In-Place

Code

#include <stdio.h>

int string_len(char *str){
    int len = 0;
    while(*str != '\0'){
        len++;
        str++;
    }
    return len;
}

void reverse_string(char *str) {
    char *end = (str + string_len(str) -1);
    while(str<end){
        *str ^= *end;
        *end ^= *str;
        *str ^= *end;
        str++;
        end--;
    }
    return;
}

int main() {
    char str[101];
    fgets(str, sizeof(str), stdin);

    // Remove newline
    int i = 0;
    while (str[i] != '\0') {
        if (str[i] == '\n') {
            str[i] = '\0';
            break;
        }
        i++;
    }

    reverse_string(str);
    printf("%s", str);
    return 0;
}

Solving Approach