leetcode No215. Kth Largest Element in an Array

Question：

Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.

For example,
Given [3,2,1,5,6,4] and k = 2, return 5.

Note: 
You may assume k is always valid, 1 ≤ k ≤ array's length.

Algorithm：

使用优先队列，优先队列是用堆实现（这里是最小堆）当堆得元素超过k个就pop一个，即pop的最小值，这样的操作结束后，优先队列的top值为堆里最小的元素，即整个数组的第k大的值，这里直接用stl实现了。

Accepted Code：

class Solution {
public:
    int findKthLargest(vector<int>& nums, int k) {
        priority_queue<int,vector<int>,greater<int>> q;
        for(int i=0;i<nums.size();i++){
            q.push(nums[i]);
            if(q.size()>k)
                q.pop();
        }
        return q.top();
    }
};