215. Kth Largest Element in an Array

题目：Kth Largest Element in an Array

原题链接：https://leetcode.com/problems/kth-largest-element-in-an-array/
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.

找出一个未排序的数组中第 k 大的元素。
题目保证 k 的合法性。
例：
[3,2,1,5,6,4] 并且 k = 2，那么第二大的元素就是5

用nth_element()函数可以直接解决，而且效率很高。

代码如下：

class Solution {public:    int findKthLargest(vector<int>& nums, int k) {        int len = nums.size();        nth_element(nums.begin(),nums.begin() + len - k, nums.end());        return nums[len - k];    }};