Reverse a String In-Place

Code

#include <stdio.h>

void reverse_string(char *str) {
    char *p1 = str;
    char *p2 = str;
    int len = 0;
    while (*p2)
        p2++;
    p2--;
    while (p2 > p1) {
        char tmp = *p1;
        *p1 = *p2;
        *p2 = tmp;
        p1++;
        p2--;
    }
}

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