703. Kth Largest Element in a Stream

原题：703. Kth Largest Element in a Stream

这道题主要考察优先队列（小堆）的用法，但是js里面没有优先队列，只能自己实现。具体可以参考leetcode上一个大神的实现：
priority-queue.js

Source Code

// Runtime: 196 ms, faster than 78.06% of JavaScript online submissions for Kth Largest Element in a Stream.
// Memory Usage: 45 MB, less than 75.00% of JavaScript online submissions for Kth Largest Element in a Stream.

var KthLargest = function(k, nums) {
    this.pq = new PriorityQueue(true);
    this.k = k;
    for(let num of nums) {
        this.add(num);
    }
};


/** 
 * @param {number} val
 * @return {number}
 */
KthLargest.prototype.add = function(val) {
  if(this.pq.size()<this.k) {
      this.pq.offer(val, val);
  }else {
      const peek = this.pq.peek();
      if(peek<val) {
          this.pq.poll();
          this.pq.offer(val, val);
      }
  }
  return this.pq.peek();//nums' length ≥ k-1, 所以不需要考虑队列长度小于k需要返回什么
};

Test Cases

test("test1", ()=>{
    expect(kthLargest.add(3)).toEqual(4);
})

test("test2", ()=>{
    expect(kthLargest.add(5)).toEqual(5);
})

test("test3", ()=>{
    expect(kthLargest.add(10)).toEqual(5);
})

test("test4", ()=>{
    expect(kthLargest.add(9)).toEqual(8);
})

test("test5", ()=>{
    expect(kthLargest.add(4)).toEqual(8);
})