[leetcode] 215. 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.

解法一：

所以如果用vector的built-in函数，这题没啥意思。

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

解法二：

还有用std::priority_queue的解法，这里queue有个top()函数，神奇。

class Solution { public: int findKthLargest(vector<int>& nums, int k) { priority_queue<int, vector<int>, greater<int>> q; for(auto &a:nums){ q.push(a); if(q.size()>k) q.pop(); } return q.top(); } };