Pair sum to 0.cpp

/*
PROBLEM:

Given a random integer array A of size N. Find and print the pair of elements in the array which sum to 0.
Array A can contain duplicate elements.
While printing a pair, print the smaller element first.
That is, if a valid pair is (6, -6) print "-6 6". There is no constraint that out of 5 pairs which have to be printed in 1st line. You can print pairs in any order, just be careful about the order of elements in a pair.
Input format :
Line 1 : Integer N (Array size)
Line 2 : Array elements (separated by space)
Output format :
Line 1 : Pair 1 elements (separated by space)
Line 2 : Pair 2 elements (separated by space)
Line 3 : and so on
Constraints :
1 <= N <= 10^6
Ai contains all non-zero values
Sample Input:
5
2 1 -2 2 3
Sample Output :
-2 2
-2 2


CODE:

*/

#include<bits/stdc++.h>
using namespace std;

void PairSum(int *input, int n){
		/* Don't write main().
     	* the input array is already passed as function argument.
     	* Don't need to return anything. Print the desired pairs in the function itself.
     	*/
      map<int,int> um;
      for(int i = 0;i<n;i++){
        um[input[i]] += 1;
      }

	  map<int,int> :: iterator it;
  	for(it = um.begin();it!=um.end();it++){
      if((*it).first>0)
      if((*it).second>0){
        if(um[0-(*it).first]){
          for(int i = 0;i<((*it).second * um[0-(*it).first]);i++){
            cout<<0-(*it).first<<" "<<(*it).first<<endl;
          }
        }
      }
    }
}