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refactor: js - heap (#686)
Co-authored-by: Mitchell Irvin <[email protected]>
1 parent f8960f5 commit 23b6d27

9 files changed

+436
-406
lines changed

‎javascript/1046-Last-Stone-Weight.js

+27-67
Original file line numberDiff line numberDiff line change
@@ -1,73 +1,33 @@
1-
class Heap {
2-
constructor(stones) {
3-
this.heap = stones;
4-
this.size = stones.length;
5-
this.heapify(0);
6-
}
7-
right(pos) {
8-
return 2 * pos + 2;
9-
}
10-
left(pos) {
11-
return 2 * pos + 1;
12-
}
13-
isleaf(pos) {
14-
if (2 * pos + 1 >= this.size) return true;
15-
return false;
16-
}
17-
swap(a, b) {
18-
let temp = this.heap[a];
19-
this.heap[a] = this.heap[b];
20-
this.heap[b] = temp;
21-
}
22-
fix(pos) {
23-
if (this.isleaf(pos)) return;
24-
let left = this.left(pos);
25-
let right = this.right(pos);
26-
let bigger = left;
27-
if (right < this.size)
28-
bigger = this.heap[left] > this.heap[right] ? left : right;
29-
if (this.heap[pos] < this.heap[bigger]) {
30-
this.swap(pos, bigger);
31-
this.fix(bigger);
32-
}
33-
}
34-
heapify(pos) {
35-
if (this.isleaf(pos)) return;
36-
this.heapify(this.left(pos));
37-
this.heapify(this.right(pos));
38-
this.fix(pos);
39-
}
40-
delete() {
41-
this.swap(0, --this.size);
42-
this.fix(0);
43-
return this.heap[0];
44-
}
45-
insert(val) {
46-
this.size++;
47-
this.heap[this.size - 1] = val;
48-
this.heapify(0);
49-
}
50-
peek() {
51-
return this.heap[0];
52-
}
53-
}
541
/**
2+
* https://leetcode.com/problems/last-stone-weight/
3+
* Time O(N * log(N)) | Space O(N)
554
* @param {number[]} stones
565
* @return {number}
576
*/
587
var lastStoneWeight = function (stones) {
59-
//use a max heap to pop off the top 2 stones at each time
60-
//if result is 0 we can do nothing
61-
//if the result is a new weight we can push it back to the heap
62-
const heap = new Heap(stones);
63-
while (heap.size > 1) {
64-
let x = heap.peek();
65-
heap.delete();
66-
let y = heap.peek();
67-
heap.delete();
68-
const res = x - y;
69-
if (res > 0) heap.insert(res);
70-
}
71-
if (heap.size) return heap.peek();
72-
return 0;
8+
const maxHeap = getMaxHeap(stones)
9+
10+
shrink(maxHeap)
11+
12+
return !maxHeap.isEmpty()
13+
? maxHeap.front().element
14+
: 0
7315
};
16+
17+
const getMaxHeap = (stones, maxHeap = new MaxPriorityQueue()) => {
18+
for (const stone of stones) {
19+
maxHeap.enqueue(stone)
20+
}
21+
22+
return maxHeap
23+
}
24+
25+
const shrink = (maxHeap) => {
26+
while (1 < maxHeap.size()) {
27+
const [ x, y ] = [ maxHeap.dequeue().element, maxHeap.dequeue().element ]
28+
const difference = x - y;
29+
30+
const isPositive = 0 < difference
31+
if (isPositive) maxHeap.enqueue(difference);
32+
}
33+
}

‎javascript/215-Kth-Largest-Element-in-an-Array.js

-39
This file was deleted.

‎javascript/295-Find-Median-From-Data-Stream.js

+56
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,56 @@
1+
/**
2+
* https://leetcode.com/problems/find-median-from-data-stream/
3+
* Your MedianFinder object will be instantiated and called as such:
4+
* var obj = new MedianFinder()
5+
* obj.addNum(num)
6+
* var param_2 = obj.findMedian()
7+
*/
8+
class MedianFinder {
9+
constructor () {
10+
this.maxHeap = new MaxPriorityQueue()
11+
this.minHeap = new MinPriorityQueue()
12+
}
13+
14+
/* Time O(log(N)) | Space (N) */
15+
insertNum (num) {
16+
this.addNum(num)
17+
}
18+
19+
addNum (num, heap = this.getHeap(num)) {
20+
heap.enqueue(num)
21+
this.rebalance()
22+
}
23+
24+
getHeap (num, { maxHeap, minHeap } = this) {
25+
const isFirst = maxHeap.isEmpty()
26+
const isGreater = num <= this.top(maxHeap);
27+
const isMaxHeap = (isFirst || isGreater);
28+
return (isMaxHeap)
29+
? maxHeap
30+
: minHeap
31+
}
32+
33+
rebalance ({ maxHeap, minHeap } = this) {
34+
const canShiftMax = (minHeap.size() + 1) < maxHeap.size()
35+
if (canShiftMax) return minHeap.enqueue(maxHeap.dequeue().element)
36+
37+
const canShiftMin = maxHeap.size() < minHeap.size()
38+
if (canShiftMin) return maxHeap.enqueue(minHeap.dequeue().element)
39+
}
40+
41+
/* Time O(1) | Space (1) */
42+
findMedian ({ maxHeap, minHeap } = this) {
43+
const isEven = maxHeap.size() === minHeap.size()
44+
return (isEven)
45+
? this.average(maxHeap, minHeap)
46+
: this.top(maxHeap)
47+
}
48+
49+
average (maxHeap, minHeap) {
50+
return (this.top(maxHeap) + this.top(minHeap)) / 2
51+
}
52+
53+
top (heap) {
54+
return heap.front()?.element || 0
55+
}
56+
}

‎javascript/295-Find-Median-from-Data-Stream.js

+48-36
Original file line numberDiff line numberDiff line change
@@ -1,44 +1,56 @@
1-
var MedianFinder = function () {
2-
this.array = [];
3-
};
4-
5-
/**
6-
* @param {number} num
7-
* @return {void}
1+
/**
2+
* https://leetcode.com/problems/find-median-from-data-stream/
3+
* Your MedianFinder object will be instantiated and called as such:
4+
* var obj = new MedianFinder()
5+
* obj.addNum(num)
6+
* var param_2 = obj.findMedian()
87
*/
9-
MedianFinder.prototype.addNum = function (num) {
10-
var low = 0;
11-
var high = this.array.length - 1;
8+
class MedianFinder {
9+
constructor () {
10+
this.maxHeap = new MaxPriorityQueue()
11+
this.minHeap = new MinPriorityQueue()
12+
}
1213

13-
while (low <= high) {
14-
var mid = Math.floor((high + low) / 2);
14+
/* Time O(log(N)) | Space (N) */
15+
insertNum (num) {
16+
this.addNum(num)
17+
}
1518

16-
if (this.array[mid] < num) {
17-
low = mid + 1;
18-
} else {
19-
high = mid - 1;
20-
}
19+
addNum (num, heap = this.getHeap(num)) {
20+
heap.enqueue(num)
21+
this.rebalance()
2122
}
2223

23-
this.array.splice(low, 0, num);
24-
};
24+
getHeap (num, { maxHeap, minHeap } = this) {
25+
const isFirst = maxHeap.isEmpty()
26+
const isGreater = num <= this.top(maxHeap);
27+
const isMaxHeap = (isFirst || isGreater);
28+
return (isMaxHeap)
29+
? maxHeap
30+
: minHeap
31+
}
2532

26-
/**
27-
* @return {number}
28-
*/
29-
MedianFinder.prototype.findMedian = function () {
30-
if (this.array.length % 2 === 0) {
31-
var mid = this.array.length / 2;
32-
return (this.array[mid] + this.array[mid - 1]) / 2;
33-
} else {
34-
var mid = Math.floor(this.array.length / 2);
35-
return this.array[mid];
33+
rebalance ({ maxHeap, minHeap } = this) {
34+
const canShiftMax = (minHeap.size() + 1) < maxHeap.size()
35+
if (canShiftMax) return minHeap.enqueue(maxHeap.dequeue().element)
36+
37+
const canShiftMin = maxHeap.size() < minHeap.size()
38+
if (canShiftMin) return maxHeap.enqueue(minHeap.dequeue().element)
3639
}
37-
};
3840

39-
/**
40-
* Your MedianFinder object will be instantiated and called as such:
41-
* var obj = new MedianFinder()
42-
* obj.addNum(num)
43-
* var param_2 = obj.findMedian()
44-
*/
41+
/* Time O(1) | Space (1) */
42+
findMedian ({ maxHeap, minHeap } = this) {
43+
const isEven = maxHeap.size() === minHeap.size()
44+
return (isEven)
45+
? this.average(maxHeap, minHeap)
46+
: this.top(maxHeap)
47+
}
48+
49+
average (maxHeap, minHeap) {
50+
return (this.top(maxHeap) + this.top(minHeap)) / 2
51+
}
52+
53+
top (heap) {
54+
return heap.front()?.element || 0
55+
}
56+
}

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