leetcode 703. 数据流中的第 K 大元素

c++

class KthLargest {
public:
    priority_queue<int, vector<int>, greater<int>> que;
    int _k;
    KthLargest(int k, vector<int>& nums) : _k(k) {
        for (int x : nums) {
            add(x);
        }
    }
    
    int add(int val) {
        que.push(val);
        if (que.size() > _k) que.pop();
        return que.top();
    }
};

js

var KthLargest = function(k, nums) {
    this.k = k;
    this.que = new MinHeap();
    for (var x of nums) {
        this.add(x);
    }
};

KthLargest.prototype.add = function(val) {
    this.que.offer(val);
    if (this.que.size() > this.k) this.que.poll();
    return this.que.peek();
};

class MinHeap {
    constructor(data = []) {
        this.data = data;
        this.comparator = (a, b) => a - b;
        this.heapify();
    }

    heapify() {
        if (this.size() < 2) return;
        for (let i = 1; i < this.size(); i++) {
        this.bubbleUp(i);
        }
    }

    peek() {
        if (this.size() === 0) return null;
        return this.data[0];
    }

    offer(value) {
        this.data.push(value);
        this.bubbleUp(this.size() - 1);
    }

    poll() {
        if (this.size() === 0) {
            return null;
        }
        const result = this.data[0];
        const last = this.data.pop();
        if (this.size() !== 0) {
            this.data[0] = last;
            this.bubbleDown(0);
        }
        return result;
    }

    bubbleUp(index) {
        while (index > 0) {
            const parentIndex = (index - 1) >> 1;
            if (this.comparator(this.data[index], this.data[parentIndex]) < 0) {
                this.swap(index, parentIndex);
                index = parentIndex;
            } else {
                break;
            }
        }
    }

    bubbleDown(index) {
        const lastIndex = this.size() - 1;
        while (true) {
            const leftIndex = index * 2 + 1;
            const rightIndex = index * 2 + 2;
            let findIndex = index;
            if (
                leftIndex <= lastIndex &&
                this.comparator(this.data[leftIndex], this.data[findIndex]) < 0
            ) {
                findIndex = leftIndex;
            }
            if (
                rightIndex <= lastIndex &&
                this.comparator(this.data[rightIndex], this.data[findIndex]) < 0
            ) {
                findIndex = rightIndex;
            }
            if (index !== findIndex) {
                this.swap(index, findIndex);
                index = findIndex;
            } else {
                break;
            }
        }
    }

  swap(index1, index2) {
        [this.data[index1], this.data[index2]] = [this.data[index2], this.data[index1]];
    }

    size() {
        return this.data.length;
    }
}