duplicate in an array of size n with numbers from 1 through n-1.

2CheckDuplicate.c

#include <stdio.h>
#define N 5
int main(){
  int array[N],i,Asum=0;
  int sum = (N *(N-1))/2;
  printf("Enter %d integer from 1 to %d,with one duplicate:"N.N-1);
  for(i=0;i<N;i++){
    scanf("%d",&array[i]);
    Asum = Asum+array[i]; 
  }
  printf("\nDuplicate number is : %d\n",Asum-sum);
}