Feat: 힙 레벨2 더 맵게

Author: ienrum

5주차/채수혁/레벨2__더_맵게.js

@@ -0,0 +1,98 @@
+class MinHeap {
+  constructor() {
+    this.heap = [];
+    this.sum = 0;
+    this.cnt = 0;
+  }
+
+  insert(value) {
+    this.heap.push(value);
+    this.heapifyUp();
+    this.sum += value;
+    this.cnt += 1;
+  }
+
+  heapifyUp() {
+    let index = this.heap.length - 1;
+    while (index > 0) {
+      let parentIndex = Math.floor((index - 1) / 2);
+
+      if (this.heap[parentIndex] <= this.heap[index]) {
+        break;
+      }
+
+      [this.heap[parentIndex], this.heap[index]] = [
+        this.heap[index],
+        this.heap[parentIndex],
+      ];
+      index = parentIndex;
+    }
+  }
+
+  extractMin() {
+    const min = this.heap[0];
+
+    const ok = this.heap.pop();
+    if (this.heap.length !== 0) this.heap[0] = ok;
+    this.heapifyDown();
+    this.sum -= min;
+    return min;
+  }
+
+  heapifyDown(index = 0) {
+    let leftChildIndex = 2 * index + 1;
+    let rightChildIndex = 2 * index + 2;
+    let smallest = index;
+
+    if (
+      leftChildIndex < this.heap.length &&
+      this.heap[leftChildIndex] < this.heap[smallest]
+    ) {
+      smallest = leftChildIndex;
+    }
+
+    if (
+      rightChildIndex < this.heap.length &&
+      this.heap[rightChildIndex] < this.heap[smallest]
+    ) {
+      smallest = rightChildIndex;
+    }
+
+    if (smallest !== index) {
+      [this.heap[smallest], this.heap[index]] = [
+        this.heap[index],
+        this.heap[smallest],
+      ];
+      this.heapifyDown(smallest);
+    }
+  }
+
+  peek() {
+    return this.heap[0];
+  }
+}
+
+function solution(scoville, K) {
+  const minHeap = new MinHeap();
+  let answer = 0;
+
+  // 스코빌 지수를 힙에 넣는다.
+  scoville.forEach((v) => minHeap.insert(v));
+
+  // 힙의 최소값이 K보다 크거나 같으면 종료
+  while (true) {
+    if (answer >= scoville.length) return -1;
+    if (minHeap.peek() >= K) return answer;
+
+    // 힙의 최소값 2개를 뽑아서 계산한 후 다시 넣는다.
+    const scovil1 = minHeap.extractMin();
+    const scovil2 = minHeap.extractMin();
+    minHeap.insert(scovil1 + scovil2 * 2);
+
+    // 횟수를 증가시킨다.
+    answer++;
+  }
+
+  // 최소힙의 최소값이 K보다 크거나 같으면 answer를 리턴
+  return minHeap.heap[0] >= K ? answer : -1;
+}