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1046-Last-Stone-Weight.ts
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1046-Last-Stone-Weight.ts
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class MaxHeap {
heap: number[]
constructor(array: number[]) {
this.heap = this.buildHeap(array)
}
buildHeap(array: number[]) {
let parentIdx = Math.floor((array.length - 2) / 2)
for (let i = parentIdx; i >= 0; i--) {
this.siftDown(i, array.length - 1, array)
}
return array
}
siftDown(idx: number, endIdx: number, heap: number[]) {
let childOneIdx = 2 * idx + 1
while (childOneIdx <= endIdx) {
let childTwoIdx = 2 * idx + 2 <= endIdx ? 2 * idx + 2 : -1
let swapIdx
if (childTwoIdx !== -1 && heap[childOneIdx] < heap[childTwoIdx]) {
swapIdx = childTwoIdx
} else swapIdx = childOneIdx
if (heap[swapIdx] > heap[idx]) {
this.swap(swapIdx, idx, heap)
idx = swapIdx
childOneIdx = 2 * idx + 1
} else return
}
}
siftUp(idx: number, heap: number[]) {
let parentIdx = Math.floor((idx - 1) / 2)
while (heap[parentIdx] < heap[idx] && idx > 0) {
this.swap(parentIdx, idx, heap)
idx = parentIdx
parentIdx = Math.floor((idx - 1) / 2)
}
}
peek() {
return this.heap[0]
}
remove() {
this.swap(this.heap.length - 1, 0, this.heap)
const removeValue = this.heap.pop()
this.siftDown(0, this.heap.length - 1, this.heap)
return removeValue
}
size() {
return this.heap.length
}
insert(value: number) {
this.heap.push(value)
this.siftUp(this.heap.length - 1, this.heap)
}
swap(i: number, j: number, arr: number[]) {
let ele = arr[i]
arr[i] = arr[j]
arr[j] = ele
}
}
function lastStoneWeight(stones: number[]): number {
const heap = new MaxHeap(stones)
while (heap.size() > 1) {
const stone1 = heap.remove()
const stone2 = heap.remove()
heap.insert(stone1 - stone2)
}
return heap.peek()
}