2024/9/20 LeetCode Hot100 堆第一题，最大堆解法

src/main/java/com/cool/hot100/heap/Num215.java

@@ -65,4 +65,40 @@ public class Num215 {
             return quickSearch(nums, j + 1, right, k);
         }
     }
+    public int findKthLargest2(int[] nums, int k) {
+        int heapSize=nums.length;
+        buildMaxHeap(nums,heapSize);
+        for(int i=nums.length-1;i>nums.length-k;i--){
+            swap(nums,0,i);
+            --heapSize;
+            maxHeapify(nums,0,heapSize);
+        }
+        return nums[0];
+    }
+
+    private void buildMaxHeap(int[]nums,int heapSize){
+        for(int i=heapSize/2;i>=0;i--){
+            maxHeapify(nums,i,heapSize);
+        }
+    }
+
+    public void maxHeapify(int[] nums, int i, int heapSize) {
+        int left = 2 * i + 1, right = 2 * i + 2, largest = i;
+        if (left < heapSize && nums[left] > nums[largest]) {
+            largest=left;
+        }
+        if(right<heapSize&&nums[right]>nums[largest]){
+            largest=right;
+        }
+        if(largest!=i){
+            swap(nums,largest,i);
+            maxHeapify(nums,largest,heapSize);
+        }
+    }
+
+    private void swap(int[] nums, int i, int j) {
+        int temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
 }