String Output shows null but why?

My Program is to Check if a String is a Palindrome. But it show while is print the string. I can't find the error..

I am using Dev-Cpp

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

main()
{
 char string[25], rev_string[25]={'\0'};
 int i, length, flag=0;

 printf("Enter a string : ");
 gets(string);

 length=strlen(string);

 for(i=length; i>=0;i--)
  {
    rev_string[length-i-1]=string[i];
    flag=0;
    printf("%s",rev_string[length-i]);
  }

 for(flag=1,i=0; i<length;i++)
  {
    if(rev_string[i]!=string[i])    
    {
        flag=0;
    }   
  }
 if (flag == 1)
   printf ("%s is a palindrome \n", string);
 else
   printf("%s is not a palindrome \n", string);

 printf("%d",length);

}