leetcode703-- Kth Largest Element in a Stream

leetcode703-- Kth Largest Element in a Stream

题目

Design a class to find the kth largest element in a stream. Note that it is the kth largest element in the sorted order, not the kth distinct element.

Your KthLargest class will have a constructor which accepts an integer k and an integer array nums, which contains initial elements from the stream. For each call to the method KthLargest.add, return the element representing the kth largest element in the stream.

Example:

int k = 3;
int[] arr = [4,5,8,2];
KthLargest kthLargest = new KthLargest(3, arr);
kthLargest.add(3);   // returns 4
kthLargest.add(5);   // returns 5
kthLargest.add(10);  // returns 5
kthLargest.add(9);   // returns 8
kthLargest.add(4);   // returns 8

Note:
You may assume that nums' length ≥ k-1 and k ≥ 1.


解答

其实之前的这几个类似的也可以用小顶堆的办法来解决,就是维护一个元素个数为k的小顶堆,超过的时候就弹出来.

class KthLargest {
public:
    KthLargest(int k, vector<int> nums) {
        for(int num: nums){
            q.push(num);
            if (q.size()>k) q.pop();
        }
        K = k;
    }
    
    int add(int val) {
        q.push(val);
        if (q.size()>K) q.pop();
        return q.top();  //返回的就是添加之后的第k大的元素。
        
    }
private:
    priority_queue<int, vector<int>, greater<int>> q;
    int K;
};


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