217th Commit

README.md

@@ -70,6 +70,10 @@ $ pnpm bench twoSum.bench.ts
 
 - [圖 (Graph)](./data-structures/graph/README.md)
 
+### Algorithms
+
+- [二分搜尋 (Binary Search)](./algorithms/binary-search/README.md)
+
 ## Basic - LeetCode 75
 
 Ace Coding Interview with 75 Qs

algorithms/binary-search/README.md

@@ -0,0 +1,33 @@
+# 二分搜尋（Binary Search）
+
+## 雙閉區間
+
+```ts
+function binarySearch(arr: number[], target: number): number {
+  let low = 0;
+  let high = arr.length - 1;
+
+  while (low <= high) {
+    const mid = Math.floor((low + high) / 2);
+
+    // 找到目標，返回索引
+    if (arr[mid] === target) return mid;
+
+    // 如果 arr[mid] 小於 target，則移動 low 指標
+    if (arr[mid] < target) {
+      low = mid + 1;
+    }
+
+    // 如果 arr[mid] 大於 target，則移動 high 指標
+    if (arr[mid] > target) {
+      high = mid - 1;
+    }
+  }
+
+  return -1; // 找不到目標
+}
+
+const sortedArray = [1, 2, 4, 7, 11, 16, 22, 29, 37, 46];
+const target = 37;
+console.log(binarySearch(sortedArray, target)); // 8
+```

algorithms/binary-search/binarySearch.ts

@@ -0,0 +1,23 @@
+function binarySearch(arr: number[], target: number): number {
+  let low = 0;
+  let high = arr.length - 1;
+
+  while (low <= high) {
+    const mid = Math.floor((low + high) / 2);
+
+    // 找到目標，返回索引
+    if (arr[mid] === target) return mid;
+
+    // 如果 arr[mid] 小於 target，則移動 low 指標
+    if (arr[mid] < target) {
+      low = mid + 1;
+    }
+
+    // 如果 arr[mid] 大於 target，則移動 high 指標
+    if (arr[mid] > target) {
+      high = mid - 1;
+    }
+  }
+
+  return -1; // 找不到目標
+}

data-structures/graph/Graph.ts

@@ -2,8 +2,15 @@ class Graph {
   // 鄰接表
   private adjacencyList: Map<string, string[]>;
 
-  constructor() {
+  constructor(initialAdjList?: { [key: string]: string[] }) {
     this.adjacencyList = new Map();
+
+    // 初始化
+    if (initialAdjList) {
+      for (const vertex in initialAdjList) {
+        this.adjacencyList.set(vertex, initialAdjList[vertex]);
+      }
+    }
   }
 
   // 新增頂點

data-structures/graph/README.md

@@ -1,6 +1,74 @@
 # 圖 (Graph)
 
+## 鄰接表 - 雜湊表方式
+
 ```ts
+class Graph {
+  // 鄰接表
+  private adjacencyList: Map<string, string[]>;
+
+  constructor(initialAdjList?: { [key: string]: string[] }) {
+    this.adjacencyList = new Map();
+
+    // 初始化
+    if (initialAdjList) {
+      for (const vertex in initialAdjList) {
+        this.adjacencyList.set(vertex, initialAdjList[vertex]);
+      }
+    }
+  }
+
+  // 新增頂點
+  addVertex(vertex: string): void {
+    if (!this.adjacencyList.has(vertex)) {
+      this.adjacencyList.set(vertex, []);
+    }
+  }
+
+  // 移除頂點
+  removeVertex(vertex: string): void {
+    if (this.adjacencyList.has(vertex)) {
+      for (const adjacentVertex of this.adjacencyList.get(vertex) || []) {
+        this.removeEdge(vertex, adjacentVertex);
+      }
+
+      this.adjacencyList.delete(vertex);
+    }
+  }
+
+  // 新增邊
+  addEdge(vertex1: string, vertex2: string): void {
+    if (this.adjacencyList.has(vertex1) && this.adjacencyList.has(vertex2)) {
+      this.adjacencyList.get(vertex1)?.push(vertex2);
+      this.adjacencyList.get(vertex2)?.push(vertex1);
+    }
+  }
+
+  // 移除邊
+  removeEdge(vertex1: string, vertex2: string): void {
+    if (this.adjacencyList.has(vertex1)) {
+      this.adjacencyList.set(
+        vertex1,
+        this.adjacencyList.get(vertex1)?.filter((v) => v !== vertex2) || [],
+      );
+    }
+
+    if (this.adjacencyList.has(vertex2)) {
+      this.adjacencyList.set(
+        vertex2,
+        this.adjacencyList.get(vertex2)?.filter((v) => v !== vertex1) || [],
+      );
+    }
+  }
+
+  // 印出圖的鄰接表
+  print(): void {
+    for (const [vertex, edges] of this.adjacencyList) {
+      console.log(`${vertex} -> ${edges.join(', ')}`);
+    }
+  }
+}
+
 const graph = new Graph();
 
 graph.addVertex('A');
@@ -39,3 +107,15 @@ flowchart LR
     C o--o D
     D o--o E
 ```
+
+### 初始化
+
+```ts
+const graph = new Graph({
+  A: ['B', 'C'],
+  B: ['A', 'D', 'E'],
+  C: ['A', 'D'],
+  D: ['B', 'C', 'E'],
+  E: ['B', 'D'],
+});
+```