Reverse String in C

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

void rev(char* s) {

    // Initialize l and r pointers
    int l = 0;
    int r = strlen(s) - 1;
    char t;

    // Swap characters till l and r meet
    while (l < r) {
      
        // Swap characters
        t = s[l];
        s[l] = s[r];
        s[r] = t;

        // Move pointers towards each other
        l++;
        r--;
    }
}

int main() {
    char s[100] = "abcde";
	
  	// Reversing s
    rev(s);
  
    printf("%s", s);
    return 0;
}

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

void rev(char* s, int l, int r) {

    // Base case is when l becomes greater than r
    if (l >= r) return;

    // Swap characters
    char t = s[l];
    s[l] = s[r];
    s[r] = t;

    // Recursively call the function with updated
  	// index pointers
    rev(s, l + 1, r - 1);
}

int main() {
    char s[100] = "abcde";

    rev(s, 0, strlen(s) - 1);
    
    printf("%s", s);
    return 0;
}

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

void rev(char* s) {
    char t[100];

    int len = strlen(s);
    int i = 0;

    // Push all characters of string s onto t
    while (len > 0) t[i++] = s[len-- - 1];
    t[i] = '\0';

    // Copying all characters from t to
  	// original string s
    strcpy(s, t);
}

int main() {
    char s[100] = "abcde";
	
  	// Reversing string s
    rev(s);
  
    printf("%s", s);
    return 0;
}

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

int main() {
    char s[] = "abcde";

    // Reversing string using strrev()
    printf("%s", strrev(s));
  
    return 0;
}