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

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 :-