Create K Smallest Elements

Author: akshayavb99

Course 2 - Data Structures in JAVA/Lecture 21 - Priority Queues II/K Smallest Elements

@@ -0,0 +1,55 @@
+/*
+You are given with an integer k and an array of integers that contain numbers in random order. Write a program to find k smallest numbers from given array. 
+You need to save them in an array and return it.
+Time complexity should be O(n * logk) and space complexity should not be more than O(k).
+Note: Order of elements in the output is not important.
+
+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 print k smallest elements. The elements in the output are separated by a single space. 
+
+Constraints:
+Time Limit: 1 sec
+
+Sample Input 1 :
+13
+2 12 9 16 10 5 3 20 25 11 1 8 6 
+4
+Sample Output 1 :
+1 2 3 5 
+*/
+
+//import java.util.ArrayList;
+import java.util.*;
+public class Solution {
+
+	public static ArrayList<Integer> kSmallest(int n, int[] input, int k) {
+		// Write your code here
+        PriorityQueue<Integer> pq = new PriorityQueue<Integer>(Collections.reverseOrder());
+        for(int i=0;i<k;i++)
+        {
+            pq.add(input[i]);
+        }
+        
+        for(int i=k;i<input.length;i++)
+        {
+            int maxVal=pq.peek();
+            if(maxVal>input[i])
+                maxVal=input[i];
+            if(maxVal!=pq.peek())
+            {
+                pq.poll();
+                pq.add(maxVal);
+            }
+        }
+        ArrayList<Integer> arr = new ArrayList<Integer>();
+        while(!pq.isEmpty())
+            arr.add(pq.poll());
+        return arr;
+
+	}
+}