1046 Last Stone Weight Solution

typescript/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()
+}