93. Reverse a String In-Place

#include <stdio.h>

void reverse_string(char *str) {
   if(str == NULL || *str == NULL) return;

   char* start = str;
   char* end = str;

   while(*end) {
        end++;
   }
   end--;

   while(start < end) {
        char temp = *start;
        *start = *end;
        *end = temp;
        start++;
        end--;
   }
}

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;
}