Reverse the string using Recursion

Given a string, Reverse the string using Recursion. [using single string]

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

/* Swap function to swap the characters */
void swap(char *x,char *y)
{
    char temp;
    temp=*x;
    *x=*y;
    *y=temp;
}

/* Reverse recursive function to reverse the received string */
void reverse(char *s,int i,int n)
{

    /* Swap the first character and the last character of the string */       
 swap((s+i),(s+n));

    /* If the starting index and ending index meet or if their difference is 1, stop swapping and print the string */       
 if(i==n || n-i==1)
    {

        printf("%s",s);
        return;
    }

    /* Recursively call the reverse the function & increment the starting index, decrement the ending index */       
 reverse(s,i+1,n-1);
}

int main(void) {

    char *s;

    int len;

    /* Dynamically allocate memory to store the input string */       
    s=(char*)malloc(sizeof(char));

    /* Get the input string from the user */                       
    scanf("%s",s);

    /* Calculate the length of the received string */             
    len=strlen(s)-1;

    /* Call the function to reverse the string */                  
    reverse(s,0,len);

    return 0;
}