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  1. import java.util.*;
  2.  
  3. class Main {
  4.     public static int countPairs(int[] nums, int target) {
  5.         Map<Integer, Integer> map = new HashMap<>();
  6.         int cnt=0;
  7.  
  8.         for (int i = 0; i < nums.length; ++i) {
  9.             int num=target-nums[i];
  10.             if(map.containsKey(num)){
  11.                 cnt++;
  12.             }
  13.             map.put(nums[i], i);
  14.         }
  15.         return cnt;
  16.     }
  17.  
  18.     public static void main(String[] args) {
  19.         Scanner sc=new Scanner(System.in);
  20.         int n=sc.nextInt();
  21.         int[] nums = new int[n];
  22.         for(int i=0;i<n;i++){
  23.             nums[i]=sc.nextInt();
  24.         }
  25.         int target = sc.nextInt();
  26.         int count=countPairs(nums,target);
  27.         System.out.println("Number of pairs with sum "+target+" : "+count);
  28.         sc.close();
  29.     }
  30. }
  31.  
Success #stdin #stdout 0.18s 60916KB
comments (?)
stdin
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5
1 2 3 4 5
6
stdout
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Number of pairs with sum 6 : 2
https://ideone.com/UiiofI
language:
Java (HotSpot 12)
created:
3 days ago
visibility:
public

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