Feat: 힙 실버2 최소 힙

Author: ienrum

5주차/채수혁/실버2__최소_힙.js

@@ -0,0 +1,111 @@
+const local_input = `
+9
+0
+12345678
+1
+2
+0
+0
+0
+0
+32
+`;
+
+const input = process.execArgv.includes("--stack-size=65536")
+  ? require("fs").readFileSync("dev/stdin").toString()
+  : local_input;
+
+const inputs = input
+  .trim()
+  .split("\n")
+  .map((v) => Number(v));
+
+const n = inputs[0];
+const arr = inputs.slice(1);
+
+class MinHeap {
+  constructor() {
+    this.heap = [];
+  }
+
+  insert(value) {
+    this.heap.push(value);
+    this.heapifyUp();
+  }
+
+  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.size() !== 0) this.heap[0] = ok;
+    this.heapifyDown();
+    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);
+    }
+  }
+  size() {
+    return this.heap.length;
+  }
+  peek() {
+    return this.heap[0];
+  }
+}
+
+const minHeap = new MinHeap();
+let result = "";
+
+arr.forEach((v) => {
+  // 0이면 최소힙에서 최솟값을 빼서 출력
+  if (v === 0) {
+    if (minHeap.size() === 0) result += 0 + "\n";
+    else result += minHeap.extractMin() + "\n";
+  } else {
+    // 0이 아니면 최소힙에 삽입
+    minHeap.insert(v);
+  }
+});
+
+// 정답 출력
+console.log(result);