Find kth smallest element in the given unsorted array

Author: m0a07xh

datastructure/array/KthSmallest.java

@@ -0,0 +1,63 @@
+package datastructure.array;
+
+import util.AlgoUtils;
+import util.ArrayUtil;
+
+/**
+ * Find kth smallest element in the given unsorted array
+ * @author Manjunath Asundi
+ */
+public class KthSmallest {
+
+ private static void buildMaxHeap(int arr[], int root, int n) {
+ int largest = root;
+ int left = (root * 2) + 1;
+ int right = (root * 2) + 2;
+ if (left <= n && arr[largest] < arr[left]) {
+ largest = left;
+ }
+ if (right <= n && arr[largest] < arr[right]) {
+ largest = right;
+ }
+ if (largest != root) {
+ int temp = arr[root];
+ arr[root] = arr[largest];
+ arr[largest] = temp;
+ buildMaxHeap(arr, largest, n);
+ }
+ }
+
+ private static int heapify(int[] arr, int k) {
+ for (int i = (k - 1) / 2; i >= 0; i--) {
+ buildMaxHeap(arr, i, k - 1);
+ }
+
+ for (int i = k; i < arr.length; i++) {
+ if (arr[i] < arr[0]) {
+ AlgoUtils.swapByIndex(arr, i, 0);
+ buildMaxHeap(arr, 0, k - 1);
+ }
+ }
+ return arr[0];
+ }
+
+ public static void main(String[] args) {
+ int[][] twoDArr = new int[][] {
+ ArrayUtil.constructRandomUniqueElementsArray(),
+ ArrayUtil.constructRandomUniqueElementsArray(),
+ ArrayUtil.constructRandomArray(),
+ ArrayUtil.constructRandomUniqueElementsArray(),
+ { 1, 11, 3, 4, 8, 5, 9, 7, 10 },
+ { 12, 2, 13, 5, 8, 11, 9, 6, 10 },
+ { 13, 3, 15, 7, 8, 9, 11, 12 },
+ { 2, 4, 6, 8, 9, 3, 7 }
+ };
+
+ for (int[] arr : twoDArr) {
+ ArrayUtil.printArray(arr);
+ int k = AlgoUtils.random(arr.length - 1) + 1;
+ System.out.println((k) + "(st/nd/rd/th) smallest number = " + heapify(arr, k));
+ System.out.println();
+ }
+ }
+}