C++ Program To Find Duplicate Element In Array Time Complexity O(n), Space Complexity O(1)

#include<iostream>
#include<stdlib.h>
using namespace std;
void repeated_element(int a[],int size)
 {
    int i,count=0;

    cout<<"Repeating Element Are : ";

    for(i=0;i<size;i++)
    {
     if(a[abs(a[i])]>0)
      a[abs(a[i])]=-a[abs(a[i])];
    else if(a[abs(a[i])]==0)
     count++;
    else
     cout<<" "<<abs(a[i]);  
    }

    if(count>1)
        cout<<" "<<count;
} 

int main()
{
 int n,i,a[20];
 
 cout<<"Enter The Size Of Array\n";
 cin>>n;
 
 cout<<"Enter The Element Of Array\n";
 for(i=0;i<n;i++)
 {
  cin>>a[i];
 }
 
 repeated_element(a,n);
 
 return 0;
}

Output:

Enter The Size Of Array

10

Enter The Element Of Array

1

2

3

1

2

3

4

5

4

6

Repeating Element Are :  1 2 3 4