Reverse the string in C programming without using temp variable

Coding:

#include<stdio.h>
#include<conio.h>
void main()
{
char s[100];
int i,j;
clrscr();
printf("\nEnter the string : ");
gets(s);
i=0;
j=strlen(s)-1;
while(i < j) 
{ 
s[i]=s[i]+s[j];
s[j]=s[i]-s[j];
s[i]=s[i]-s[j--];
i++;
} 
// using built-in function: 
//n=strrev(s);
printf("\nReverse string is : %s",s);
getch();
}


Output: