Create Pairs with difference K

Author: akshayavb99

Course 2 - Data Structures in JAVA/Lecture 16 - HashMaps/Pairs with difference K

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+/*
+You are given with an array of integers and an integer K. You have to find and print the count of all such pairs which have difference K.
+Note: Take absolute difference between the elements of the array.
+
+Input Format:
+The first line of input contains an integer, that denotes the value of the size of the array. Let us denote it with the symbol n.
+The following line contains n space separated integers, that denote the value of the elements of the array.
+The following line contains an integer, that denotes the value of K.
+
+Output format :
+The first and only line of output contains count of all such pairs which have an absolute difference of K. 
+
+Constraints :
+0 <= n <= 10^4
+Time Limit: 1 sec
+
+Sample Input 1 :
+4 
+5 1 2 4
+3
+Sample Output 1 :
+2
+
+Sample Input 2 :
+4
+4 4 4 4 
+0
+Sample Output 2 :
+6
+*/
+import java.util.HashMap;
+public class Solution {
+
+	public static int getPairsWithDifferenceK(int arr[], int k) {
+		//Write your code here
+        HashMap<Integer,Integer> map = new HashMap<>();
+        for(int key:arr)
+        {	
+            if(map.containsKey(key))
+        	{
+            	map.put(key,map.get(key)+1);
+        	}
+            else
+            {
+                map.put(key,1);
+            }   
+        }
+        /*
+        for (Integer i: map.keySet())
+        {
+            System.out.println(i + ": " + map.get(i));
+        }
+        System.out.println();
+        */
+        int countPairs=0;
+        if (k==0)
+        {
+            for (Integer i: map.keySet())
+        	{
+                int val=map.get(i);
+            	countPairs=countPairs+(val*(val-1))/2;
+        	}
+            return countPairs;
+        }
+        
+        for (Integer i: map.keySet())
+        {
+            //System.out.println("Current element: "+i);
+            //System.out.println("Need to find: "+(i-k)+", "+(i+k));
+            if (map.containsKey(k+i))
+            {
+                //System.out.println("Found " + (k+i));
+            	countPairs=countPairs+(map.get(i)*map.get(k+i));   
+                //System.out.println("Current count of pairs: "+countPairs);
+            }
+            if (map.containsKey(i-k))
+            {
+                //System.out.println("Found " + (i-k));
+            	countPairs=countPairs+(map.get(i)*map.get(i-k));   
+                //System.out.println("Current count of pairs: "+countPairs);
+            }
+            //System.out.println();
+        }
+        countPairs=countPairs/2;
+        return countPairs;
+	}
+}