106차 2번 문제풀이

Author: Eric

live10/test106/문제2/황장현.js

@@ -0,0 +1,113 @@
+class MinHeap {
+  constructor() {
+    this.heap = [];
+  }
+  push(value) {
+    this.heap.push(value);
+    this.bubbleUp();
+  }
+
+  pop() {
+    if (this.heap.length === 1) return this.heap.pop();
+    const min = this.heap[0];
+    this.heap[0] = this.heap.pop();
+    this.bubbleDown();
+    return min;
+  }
+
+  bubbleUp() {
+    let index = this.heap.length - 1;
+
+    while (index > 0) {
+      const 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;
+    }
+  }
+
+  bubbleDown() {
+    let index = 0;
+    const length = this.heap.length;
+
+    while (true) {
+      const left = 2 * index + 1;
+      const right = 2 * index + 2;
+      let smallest = index;
+
+      if (left < length && this.heap[left] < this.heap[smallest]) {
+        smallest = left;
+      }
+
+      if (right < length && this.heap[right] < this.heap[smallest]) {
+        smallest = right;
+      }
+
+      if (smallest === index) break;
+
+      [this.heap[index], this.heap[smallest]] = [
+        this.heap[smallest],
+        this.heap[index],
+      ];
+
+      index = smallest;
+    }
+  }
+
+  least() {
+    return this.heap[0];
+  }
+
+  size() {
+    return this.heap.length;
+  }
+}
+
+const input = require('fs')
+  .readFileSync(process.platform === 'linux' ? '/dev/stdin' : './input.txt')
+  .toString()
+  .trim()
+  .split('\n')
+  .map((el) => el.split(' ').map(Number));
+
+function solution(input) {
+  const [N, M] = input[0];
+  const adjList = Array.from({ length: N + 1 }, () => []);
+
+  for (let i = 1; i <= M; i++) {
+    const [A, B, C] = input[i];
+    adjList[A].push([B, C]);
+    adjList[B].push([A, C]);
+  }
+
+  function dijkstra(start) {
+    const distances = Array(N + 1).fill(Infinity);
+    const minHeap = new MinHeap();
+    minHeap.push([0, start]);
+    distances[start] = 0;
+
+    while (minHeap.size() > 0) {
+      const [currentCost, currentNode] = minHeap.pop();
+
+      if (currentCost > distances[currentNode]) continue;
+
+      for (const [nextNode, nextCost] of adjList[currentNode]) {
+        const newCost = currentCost + nextCost;
+
+        if (newCost < distances[nextNode]) {
+          distances[nextNode] = newCost;
+          minHeap.push([newCost, nextNode]);
+        }
+      }
+    }
+
+    return distances[N];
+  }
+
+  return dijkstra(1);
+}
+
+console.log(solution(input));