leetcode 215. Kth Largest Element in an Array

Posted 2020-10-04 いいえ敗者

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.

求第k大的数。用小堆去维护

这题几年前做过...

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) {
            if (q.empty()) q.push(nums[i]);
            else {
                int x = q.top();
                if (q.size() < k) q.push(nums[i]);
                else {
                    if (nums[i] > x) q.pop(), q.push(nums[i]);
                }
            }
        }
        if (q.empty()) return 0;
        return q.top();
    }
};