Leetcode215

dsa-solutions/lc-solutions/0200-0299/0215-kth-largest-element-in-an-array.md

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+---
+id: kth-largest-element-in-an-array
+title: Kth Largest Element in an Array (LeetCode)
+sidebar_label: 0215-KthLargestElementInAnArray
+description: Find the kth largest element in an unsorted array. Note that it is the kth largest element in sorted order, not the kth distinct element.
+---
+
+## Problem Description
+
+| Problem Statement | Solution Link | LeetCode Profile |
+| :---------------- | :------------ | :--------------- |
+| [Kth Largest Element in an Array](https://leetcode.com/problems/kth-largest-element-in-an-array/) | [Kth Largest Element in an Array Solution on LeetCode](https://leetcode.com/problems/kth-largest-element-in-an-array/solutions/) | [vaishu_1904](https://leetcode.com/u/vaishu_1904/) |
+
+## Problem Description
+
+Given an integer array `nums` and an integer `k`, return the `k`th largest element in the array.
+
+Note that it is the `k`th largest element in sorted order, not the `k`th distinct element.
+
+### Examples
+
+#### Example 1
+
+- **Input:** `nums = [3,2,1,5,6,4]`, `k = 2`
+- **Output:** `5`
+- **Explanation:** The second largest element is 5.
+
+#### Example 2
+
+- **Input:** `nums = [3,2,3,1,2,4,5,5,6]`, `k = 4`
+- **Output:** `4`
+- **Explanation:** The fourth largest element is 4.
+
+### Constraints
+
+- `1 <= k <= nums.length <= 10^4`
+- $-10^4 <= nums[i] <= 10^4$
+
+### Approach
+
+To find the `k`th largest element in an unsorted array, we can use various methods such as sorting, using a min-heap, or using Quickselect algorithm. Here are the approaches:
+
+1. **Sorting**:
+   - Sort the array and return the element at index `len(nums) - k`.
+
+2. **Min-Heap**:
+   - Maintain a min-heap of size `k`.
+   - Iterate through the array and maintain the heap with the largest `k` elements.
+   - The root of the heap will be the `k`th largest element.
+
+3. **Quickselect**:
+   - Use a partition-based method to find the `k`th largest element in `O(n)` average time complexity.
+
+### Solution Code
+
+#### Python
+
+```python
+import heapq
+
+class Solution:
+    def findKthLargest(self, nums, k):
+        return heapq.nlargest(k, nums)[-1]
+```
+
+#### Java
+
+```java
+import java.util.PriorityQueue;
+
+class Solution {
+    public int findKthLargest(int[] nums, int k) {
+        PriorityQueue<Integer> minHeap = new PriorityQueue<>();
+        for (int num : nums) {
+            minHeap.offer(num);
+            if (minHeap.size() > k) {
+                minHeap.poll();
+            }
+        }
+        return minHeap.peek();
+    }
+}
+```
+
+#### C++
+
+```c++
+#include <queue>
+#include <vector>
+
+class Solution {
+public:
+    int findKthLargest(vector<int>& nums, int k) {
+        priority_queue<int, vector<int>, greater<int>> minHeap;
+        for (int num : nums) {
+            minHeap.push(num);
+            if (minHeap.size() > k) {
+                minHeap.pop();
+            }
+        }
+        return minHeap.top();
+    }
+};
+```
+
+### Conclusion
+The above solutions effectively find the kth largest element in an array using different methods. 
+The min-heap approach provides an efficient solution with a time complexity of O(n log k), making it 
+suitable for larger inputs while ensuring the correct element is found. Each implementation handles 
+edge cases and constraints effectively, providing robust solutions across various programming 
+languages.