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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.             // nums[i] - nums[j] == target ----> nums[i] = nums[j] + target
  10.             int num=target+nums[i];
  11.             if(map.containsKey(num)){
  12.                 cnt+=map.get(num);
  13.             }
  14.             map.put(nums[i], map.getOrDefault(nums[i],0)+1);
  15.         }
  16.         return cnt;
  17.     }
  18.  
  19.     public static void main(String[] args) {
  20.         Scanner sc=new Scanner(System.in);
  21.         int n=sc.nextInt();
  22.         int[] nums = new int[n];
  23.         for(int i=0;i<n;i++){
  24.             nums[i]=sc.nextInt();
  25.         }
  26.         int target = sc.nextInt();
  27.         int count=countPairs(nums,target);
  28.         System.out.println("Number of pairs with difference "+target+" : "+count);
  29.         sc.close();
  30.     }
  31. }
Success #stdin #stdout 0.23s 58788KB
comments (?)
stdin 
5
1 5 3 4 2
2
stdout 
Number of pairs with difference 2 : 2
https://ideone.com/m4QuWH
language:
Java (HotSpot 12)
created:
3 days ago
visibility:
public

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