**Problem :-**Find Duplicates In O(n) Time And O(1) Extra Space.Given An array Of n Elements With Any Of These Numbers Appearing Any Number Of Times. Find These Repeating Numbers In O(n) And Using Only Constant Memory Space.

**Example**

Let n Be 9 And Array Be {0,2,3,2,3,0,9,9,7}, The OUTPUT Should Be 2, 3 ,9 And 0.

**Solution :-**

#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 :-**

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