leetcode——【最小、大堆实现】

堆是一种数据结构，就是每个节点根据某种规则排序， 从根节点往下都符合某种规律，根节点的值比所有节点的值都大， 称为最大堆；根节点的值比所有节点的值都小， 称为最小堆。

class Solution {
public:
    void adjust_heap(vector& nums, int father, int len) {
        int left = 2 * father + 1;
        int right = 2 * father + 2;
        int max = father;
        if (left < len && nums[left] > nums[max])
            max = left;
        if (right < len && nums[right] > nums[max])
            max = right;
        if (max != father) {
            swap(nums[father], nums[max]);
            adjust_heap(nums, max, len);
        }
    }

    void buildMaxHeap(vector& nums, int len) {
        for (int i = len / 2; i >= 0; --i) {
            adjust_heap(nums, i, len);
        }
    }


    int findKthLargest(vector& nums, int k) {
        int len = nums.size();
        buildMaxHeap(nums, len);
        for (int i = 0; i < k; ++i) {
            swap(nums[0], nums[nums.size() - 1 - i]);
            --len;
            adjust_heap(nums, 0, len);
        }
        return nums[0];
    }
};