LeetCode --- 703. Kth Largest Element in a Stream-优快云博客

本文介绍了一种使用优先队列（小顶堆）实现KthLargest类的方法，该类能够找到数据流中的第k大元素。通过实例演示了如何在数据流中添加元素并获取当前的第k大元素。

703. Kth Largest Element in a Stream

Difficulty: Easy

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.

Solution

思路

使用优先队列，小顶堆，
priority_queue<int, vector<int>, greater<int> > pq;
保存k个数，返回队列头部即可。
Language: C++

class KthLargest {
public:
    KthLargest(int k, vector<int>& nums) {
        size = k;
        for(auto i : nums){
            pq.push(i);
            if (pq.size() > k)
                pq.pop();
        }
    }
    
    int add(int val) {
        pq.push(val);
        if (pq.size() > size) pq.pop();
        return pq.top();
    }
private:
    priority_queue<int, vector<int>, greater<int> > pq;
    int size;
};

/**
 * Your KthLargest object will be instantiated and called as such:
 * KthLargest* obj = new KthLargest(k, nums);
 * int param_1 = obj->add(val);
 */