solves kth largest element in array in java

Author: anishLearnsToCode

README.md

@@ -172,7 +172,7 @@
 | 210  | [Course Schedule II](https://leetcode.com/problems/course-schedule-ii)                                                                                    |                                                                                                                                                                                      |                                                                                                                                   |
 | 211  | [Design Add and Search Words Data Structure](https://leetcode.com/problems/design-add-and-search-words-data-structure)                                    |                                                                                                                                                                                      |                                                                                                                                   |
 | 213  | [House Robber II](https://leetcode.com/problems/house-robber-ii)                                                                                          |                                                                                                                                                                                      |                                                                                                                                   |
-| 215  | [Kth Largest Element in an Array](https://leetcode.com/problems/kth-largest-element-in-an-array)                                                          |                                                                                                                                                                                      |                                                                                                                                   |
+| 215  | [Kth Largest Element in an Array](https://leetcode.com/problems/kth-largest-element-in-an-array)                                                          |                                                           [![Java](assets/java.png)](src/KthLargestElementInAnArray.java)                                                            |                                                                                                                                   |
 | 216  | [Combination Sum III](https://leetcode.com/problems/combination-sum-iii)                                                                                  |                                                                                                                                                                                      |                                                                                                                                   |
 | 217  | [Contains Duplicate](https://leetcode.com/problems/contains-duplicate)                                                                                    |                                 [![Java](assets/java.png)](src/ContainsDuplicate.java) [![Python](assets/python.png)](python/contains_duplicate.py)                                  |                                                                                                                                   |
 | 219  | [Contains Duplicate II](https://leetcode.com/problems/contains-duplicate-ii)                                                                              |                               [![Java](assets/java.png)](src/ContainsDuplicateII.java) [![Python](assets/python.png)](python/contains_duplicate_ii.py)                               |                                                                                                                                   |

src/KthLargestElementInAnArray.java

@@ -0,0 +1,34 @@
+// https://leetcode.com/problems/kth-largest-element-in-an-array
+// T: O(n)
+// S: O(1)
+
+public class KthLargestElementInAnArray {
+    public int findKthLargest(int[] nums, int k) {
+        int partitionIndex = nums.length - k;
+        for (int left = 0, right = nums.length - 1, j ; left < right ; ) {
+            j = partition(nums, left, right);
+            if (j == partitionIndex) return nums[partitionIndex];
+            else if (j < partitionIndex) left = j + 1;
+            else right = j - 1;
+        }
+        return nums[partitionIndex];
+    }
+
+    private int partition(int[] array, int left, int right) {
+        int pivot = array[right], i = left - 1;
+        for (int j = left ; j < right ; j++) {
+            if (array[j] < pivot) {
+                i++;
+                swap(array, i, j);
+            }
+        }
+        swap(array, i + 1, right);
+        return i + 1;
+    }
+
+    private void swap(int[] array, int i, int j) {
+        int temp = array[i];
+        array[i] = array[j];
+        array[j] = temp;
+    }
+}