手写优先队列

发表于 | 更新于: |
字数统计: 916

优先队列一般是用堆来实现的，查询复杂度是 O(1)，插入和删除的复杂度是 O(logN)。堆结构就是一个完全二叉树，完全二叉树可以用数组实现。

测试场景：215. 数组中的第 K 个最大元素

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
class PriorityQueue1<T> {
  arr: T[];
  compare: (a: T, b: T) => number;
  constructor(props: { compare: (a: T, b: T) => number }) {
    const { compare } = props;
    this.compare = compare;
    this.arr = [];
  }
  swap(arr, index1, index2) {
    const temp = arr[index1];
    arr[index1] = arr[index2];
    arr[index2] = temp;
  }
  enqueue(a) {
    this.arr.push(a);
    this.bubbleUp(this.arr.length - 1);
  }
  dequeue() {
    this.delete(0);
  }
  bubbleUp(index) {
    if (this.arr.length <= 1 || index <= 0) {
      return;
    }
    const pre = Math.floor((index - 1) / 2);
    if (this.compare(this.arr[index], this.arr[pre]) > 0) {
      this.swap(this.arr, pre, index);
      this.bubbleUp(pre);
    }
  }
  delete(index) {
    this.swap(this.arr, index, this.arr.length - 1);
    this.arr.pop();
    this.sinkDown(index);
  }
  sinkDown(index) {
    if (this.arr.length <= 1 || index >= this.arr.length - 1) {
      return;
    }
    if (
      (index * 2 + 1 < this.arr.length &&
        this.compare(this.arr[index], this.arr[index * 2 + 1]) < 0) ||
      (index * 2 + 2 < this.arr.length &&
        this.compare(this.arr[index], this.arr[index * 2 + 2]) < 0)
    ) {
      if (
        index * 2 + 2 >= this.arr.length ||
        this.compare(this.arr[index * 2 + 1], this.arr[index * 2 + 2]) > 0
      ) {
        this.swap(this.arr, index, index * 2 + 1);
        this.sinkDown(index * 2 + 1);
      } else {
        this.swap(this.arr, index, index * 2 + 2);
        this.sinkDown(index * 2 + 2);
      }
    }
  }
  front() {
    return this.arr[0];
  }
  size() {
    return this.arr.length;
  }
}

function findKthLargest(nums: number[], k: number): number {
  // PriorityQueue1
  const pq = new PriorityQueue1({ compare: (a: number, b: number) => a - b });
  for (let i = 0; i < nums.length; i++) {
    pq.enqueue(nums[i]);
  }
  for (let i = k - 1; i >= 1; i--) {
    pq.dequeue();
  }
  return pq.front();
}

测试场景 2：2034. 股票价格波动

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
class PriorityQueue1<T> {
  arr: T[];
  compare: (a: T, b: T) => number;
  constructor(props: { compare: (a: T, b: T) => number }) {
    const { compare } = props;
    this.compare = compare;
    this.arr = [];
  }
  swap(arr, index1, index2) {
    const temp = arr[index1];
    arr[index1] = arr[index2];
    arr[index2] = temp;
  }
  enqueue(a) {
    this.arr.push(a);
    this.bubbleUp(this.arr.length - 1);
  }
  dequeue() {
    this.delete(0);
  }
  bubbleUp(index) {
    if (this.arr.length <= 1 || index <= 0) {
      return;
    }
    const pre = Math.floor((index - 1) / 2);
    if (this.compare(this.arr[index], this.arr[pre]) > 0) {
      this.swap(this.arr, pre, index);
      this.bubbleUp(pre);
    }
  }
  delete(index) {
    this.swap(this.arr, index, this.arr.length - 1);
    this.arr.pop();
    this.sinkDown(index);
  }
  sinkDown(index) {
    if (this.arr.length <= 1 || index >= this.arr.length - 1) {
      return;
    }
    if (
      (index * 2 + 1 < this.arr.length &&
        this.compare(this.arr[index], this.arr[index * 2 + 1]) < 0) ||
      (index * 2 + 2 < this.arr.length &&
        this.compare(this.arr[index], this.arr[index * 2 + 2]) < 0)
    ) {
      if (
        index * 2 + 2 >= this.arr.length ||
        this.compare(this.arr[index * 2 + 1], this.arr[index * 2 + 2]) > 0
      ) {
        this.swap(this.arr, index, index * 2 + 1);
        this.sinkDown(index * 2 + 1);
      } else {
        this.swap(this.arr, index, index * 2 + 2);
        this.sinkDown(index * 2 + 2);
      }
    }
  }
  front() {
    return this.arr[0];
  }
  size() {
    return this.arr.length;
  }
}

interface Data {
  index: number;
  value: number;
}

class StockPrice {
  priceArr: number[];
  maxPriorityQueue: PriorityQueue1<{ index: number; value: number }>;
  minPriorityQueue: PriorityQueue1<{ index: number; value: number }>;
  constructor() {
    this.priceArr = [];
    this.maxPriorityQueue = new PriorityQueue1({
      compare: (a: Data, b: Data) => a.value - b.value,
    });
    this.minPriorityQueue = new PriorityQueue1({
      compare: (a: Data, b: Data) => b.value - a.value,
    });
  }

  update(timestamp: number, price: number): void {
    this.priceArr[timestamp] = price;
    this.maxPriorityQueue.enqueue({ index: timestamp, value: price });
    this.minPriorityQueue.enqueue({ index: timestamp, value: price });
  }

  current(): number {
    return this.priceArr[this.priceArr.length - 1];
  }

  maximum(): number {
    while (
      this.maxPriorityQueue.front().value !==
      this.priceArr[this.maxPriorityQueue.front().index]
    ) {
      this.maxPriorityQueue.dequeue();
    }
    return this.maxPriorityQueue.front().value;
  }

  minimum(): number {
    while (
      this.minPriorityQueue.front().value !==
      this.priceArr[this.minPriorityQueue.front().index]
    ) {
      this.minPriorityQueue.dequeue();
    }
    return this.minPriorityQueue.front().value;
  }
}

/**
 * Your StockPrice object will be instantiated and called as such:
 * var obj = new StockPrice()
 * obj.update(timestamp,price)
 * var param_2 = obj.current()
 * var param_3 = obj.maximum()
 * var param_4 = obj.minimum()
 */