Merge branch 'master' into binary_search_tree

codes/typescript/chapter_array_and_linkedlist/array.ts

@@ -1,4 +1,4 @@
-/*
+/**
  * File: array.ts
  * Created Time: 2022-12-04
  * Author: Justin (xiefahit@gmail.com)

codes/typescript/chapter_array_and_linkedlist/linked_list.ts

@@ -1,4 +1,4 @@
-/*
+/**
  * File: linked_list.ts
  * Created Time: 2022-12-10
  * Author: Justin (xiefahit@gmail.com)

codes/typescript/chapter_array_and_linkedlist/list.ts

@@ -1,4 +1,4 @@
-/*
+/**
  * File: list.ts
  * Created Time: 2022-12-10
  * Author: Justin (xiefahit@gmail.com)

codes/typescript/chapter_array_and_linkedlist/my_list.ts

@@ -1,4 +1,4 @@
-/*
+/**
  * File: my_list.ts
  * Created Time: 2022-12-11
  * Author: Justin (xiefahit@gmail.com)

codes/typescript/chapter_computational_complexity/leetcode_two_sum.ts

@@ -1,4 +1,4 @@
-/*
+/**
  * File: leetcode_two_sum.ts
  * Created Time: 2022-12-15
  * Author: gyt95 (gytkwan@gmail.com) 

codes/typescript/chapter_computational_complexity/time_complexity.ts

@@ -0,0 +1,155 @@
+/**
+ * File: time_complexity.ts
+ * Created Time: 2023-01-02
+ * Author: RiverTwilight (contact@rene.wang)
+ */
+
+/* 常数阶 */
+function constant(n: number): number {
+    let count = 0;
+    const size = 100000;
+    for (let i = 0; i < size; i++) count++;
+    return count;
+}
+
+/* 线性阶 */
+function linear(n: number): number {
+    let count = 0;
+    for (let i = 0; i < n; i++) count++;
+    return count;
+}
+
+/* 线性阶（遍历数组） */
+function arrayTraversal(nums: number[]): number {
+    let count = 0;
+    // 循环次数与数组长度成正比
+    for (let i = 0; i < nums.length; i++) {
+        count++;
+    }
+    return count;
+}
+
+/* 平方阶 */
+function quadratic(n: number): number {
+    let count = 0;
+    // 循环次数与数组长度成平方关系
+    for (let i = 0; i < n; i++) {
+        for (let j = 0; j < n; j++) {
+            count++;
+        }
+    }
+    return count;
+}
+
+/* 平方阶（冒泡排序） */
+function bubbleSort(nums: number[]): number {
+    let count = 0; // 计数器
+    // 外循环：待排序元素数量为 n-1, n-2, ..., 1
+    for (let i = nums.length - 1; i > 0; i--) {
+        // 内循环：冒泡操作
+        for (let j = 0; j < i; j++) {
+            if (nums[j] > nums[j + 1]) {
+                // 交换 nums[j] 与 nums[j + 1]
+                let tmp = nums[j];
+                nums[j] = nums[j + 1];
+                nums[j + 1] = tmp;
+                count += 3; // 元素交换包含 3 个单元操作
+            }
+        }
+    }
+    return count;
+}
+
+/* 指数阶（循环实现） */
+function exponential(n: number): number {
+    let count = 0,
+        base = 1;
+    // cell 每轮一分为二，形成数列 1, 2, 4, 8, ..., 2^(n-1)
+    for (let i = 0; i < n; i++) {
+        for (let j = 0; j < base; j++) {
+            count++;
+        }
+        base *= 2;
+    }
+    // count = 1 + 2 + 4 + 8 + .. + 2^(n-1) = 2^n - 1
+    return count;
+}
+
+/* 指数阶（递归实现） */
+function expRecur(n: number): number {
+    if (n == 1) return 1;
+    return expRecur(n - 1) + expRecur(n - 1) + 1;
+}
+
+/* 对数阶（循环实现） */
+function logarithmic(n: number): number {
+    let count = 0;
+    while (n > 1) {
+        n = n / 2;
+        count++;
+    }
+    return count;
+}
+
+/* 对数阶（递归实现） */
+function logRecur(n: number): number {
+    if (n <= 1) return 0;
+    return logRecur(n / 2) + 1;
+}
+
+/* 线性对数阶 */
+function linearLogRecur(n: number): number {
+    if (n <= 1) return 1;
+    let count = linearLogRecur(n / 2) + linearLogRecur(n / 2);
+    for (let i = 0; i < n; i++) {
+        count++;
+    }
+    return count;
+}
+
+/* 阶乘阶（递归实现） */
+function factorialRecur(n: number): number {
+    if (n == 0) return 1;
+    let count = 0;
+    // 从 1 个分裂出 n 个
+    for (let i = 0; i < n; i++) {
+        count += factorialRecur(n - 1);
+    }
+    return count;
+}
+
+/* Driver Code */
+// 可以修改 n 运行，体会一下各种复杂度的操作数量变化趋势
+const n = 8;
+console.log("输入数据大小 n = " + n);
+
+let count = constant(n);
+console.log("常数阶的计算操作数量 = " + count);
+
+count = linear(n);
+console.log("线性阶的计算操作数量 = " + count);
+count = arrayTraversal(new Array(n));
+console.log("线性阶（遍历数组）的计算操作数量 = " + count);
+
+count = quadratic(n);
+console.log("平方阶的计算操作数量 = " + count);
+var nums = new Array(n);
+for (let i = 0; i < n; i++) nums[i] = n - i; // [n,n-1,...,2,1]
+count = bubbleSort(nums);
+console.log("平方阶（冒泡排序）的计算操作数量 = " + count);
+
+count = exponential(n);
+console.log("指数阶（循环实现）的计算操作数量 = " + count);
+count = expRecur(n);
+console.log("指数阶（递归实现）的计算操作数量 = " + count);
+
+count = logarithmic(n);
+console.log("对数阶（循环实现）的计算操作数量 = " + count);
+count = logRecur(n);
+console.log("对数阶（递归实现）的计算操作数量 = " + count);
+
+count = linearLogRecur(n);
+console.log("线性对数阶（递归实现）的计算操作数量 = " + count);
+
+count = factorialRecur(n);
+console.log("阶乘阶（递归实现）的计算操作数量 = " + count);

codes/typescript/chapter_computational_complexity/worst_best_time_complexity.ts

@@ -0,0 +1,45 @@
+/*
+ * File: worst_best_time_complexity.ts
+ * Created Time: 2023-01-05
+ * Author: RiverTwilight (contact@rene.wang)
+ */
+
+/* 生成一个数组，元素为 { 1, 2, ..., n }，顺序被打乱 */
+function randomNumbers(n: number): number[] {
+    let nums = Array(n);
+    // 生成数组 nums = { 1, 2, 3, ..., n }
+    for (let i = 0; i < n; i++) {
+        nums[i] = i + 1;
+    }
+    // 随机打乱数组元素
+    for (let i = 0; i < n; i++) {
+        let r = Math.floor(Math.random() * (i + 1));
+        let temp = nums[i];
+        nums[i] = nums[r];
+        nums[r] = temp;
+    }
+    return nums;
+}
+
+/* 查找数组 nums 中数字 1 所在索引 */
+function findOne(nums: number[]): number {
+    for (let i = 0; i < nums.length; i++) {
+        if (nums[i] === 1) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+/* Driver Code */
+function main(): void {
+    for (let i = 0; i < 10; i++) {
+        let n = 100;
+        let nums = randomNumbers(n);
+        let index = findOne(nums);
+        console.log(
+            "\n数组 [ 1, 2, ..., n ] 被打乱后 = [" + nums.join(", ") + "]"
+        );
+        console.log("数字 1 的索引为 " + index);
+    }
+}

codes/typescript/chapter_hashing/array_hash_map.ts

@@ -1,4 +1,4 @@
-/*
+/**
  * File: array_hash_map.ts
  * Created Time: 2022-12-20
  * Author: Daniel (better.sunjian@gmail.com)

codes/typescript/chapter_hashing/hash_map.ts

@@ -1,4 +1,4 @@
-/*
+/**
  * File: hash_map.ts
  * Created Time: 2022-12-20
  * Author: Daniel (better.sunjian@gmail.com)

codes/typescript/chapter_sorting/merge_sort.ts

@@ -23,10 +23,10 @@ function merge(nums: number[], left: number, mid: number, right: number): void {
         // 若“左子数组已全部合并完”，则选取右子数组元素，并且 j++
         if (i > leftEnd) {
             nums[k] = tmp[j++];
-            // 否则，若“右子数组已全部合并完”或“左子数组元素 < 右子数组元素”，则选取左子数组元素，并且 i++
+            // 否则，若“右子数组已全部合并完”或“左子数组元素 <= 右子数组元素”，则选取左子数组元素，并且 i++
         } else if (j > rightEnd || tmp[i] <= tmp[j]) {
             nums[k] = tmp[i++];
-            // 否则，若“左子数组元素 > 右子数组元素”，则选取右子数组元素，并且 j++
+            // 否则，若“左右子数组都未全部合并完”且“左子数组元素 > 右子数组元素”，则选取右子数组元素，并且 j++
         } else {
             nums[k] = tmp[j++];
         }

codes/typescript/chapter_tree/binary_search_tree.ts

@@ -120,7 +120,7 @@ function remove(num: number): TreeNode | null {
     // 子结点数量 = 2
     else {
         // 获取中序遍历中 cur 的下一个结点
-        let next = min(cur.right);
+        let next = getInOrderNext(cur.right);
         let tmp = next!.val;
         // 递归删除结点 nex
         remove(next!.val);
@@ -130,8 +130,8 @@ function remove(num: number): TreeNode | null {
     return cur;
 }
 
-/* 获取最小结点 */
-function min(root: TreeNode | null): TreeNode | null {
+/* 获取中序遍历中的下一个结点（仅适用于 root 有左子结点的情况） */
+function getInOrderNext(root: TreeNode | null): TreeNode | null {
     if (root === null) {
         return null;
     }

codes/typescript/chapter_tree/binary_tree_bfs.ts

@@ -30,7 +30,7 @@ function hierOrder(root: TreeNode | null): number[] {
 /* Driver Code */
 /* 初始化二叉树 */
 // 这里借助了一个从数组直接生成二叉树的函数
-var root = arrToTree([1, 2, 3, 4, 5, 6, 7, null, null, null, null, null, null, null, null]);
+var root = arrToTree([1, 2, 3, 4, 5, 6, 7]);
 console.log('\n初始化二叉树\n');
 printTree(root);
 

codes/typescript/chapter_tree/binary_tree_dfs.ts

@@ -47,7 +47,7 @@ function postOrder(root: TreeNode | null): void {
 /* Driver Code */
 /* 初始化二叉树 */
 // 这里借助了一个从数组直接生成二叉树的函数
-const root = arrToTree([1, 2, 3, 4, 5, 6, 7, null, null, null, null, null, null, null, null]);
+const root = arrToTree([1, 2, 3, 4, 5, 6, 7]);
 console.log('\n初始化二叉树\n');
 printTree(root);
 

codes/typescript/module/ListNode.ts

@@ -1,4 +1,4 @@
-/*
+/**
  * File: ListNode.ts
  * Created Time: 2022-12-10
  * Author: Justin (xiefahit@gmail.com)

codes/typescript/module/PrintUtil.ts

@@ -1,4 +1,4 @@
-/*
+/**
  * File: PrintUtil.ts
  * Created Time: 2022-12-13
  * Author: Justin (xiefahit@gmail.com)

codes/typescript/module/TreeNode.ts

@@ -1,4 +1,4 @@
-/*
+/**
  * File: TreeNode.ts
  * Created Time: 2022-12-13
  * Author: Justin (xiefahit@gmail.com)
@@ -20,7 +20,7 @@ class TreeNode {
 }
 
 /**
- * Generate a binary tree with an array
+ * Generate a binary tree given an array
  * @param arr
  * @return
  */
@@ -31,19 +31,19 @@ function arrToTree(arr: (number | null)[]): TreeNode | null {
 
     const root = new TreeNode(arr[0] as number);
     const queue = [root];
-    let i = 1;
+    let i = 0;
     while (queue.length) {
         let node = queue.shift() as TreeNode;
+        if (++i >= arr.length) break;
         if (arr[i] !== null) {
             node.left = new TreeNode(arr[i] as number);
             queue.push(node.left);
         }
-        i++;
+        if (++i >= arr.length) break;
         if (arr[i] !== null) {
             node.right = new TreeNode(arr[i] as number);
             queue.push(node.right);
         }
-        i++;
     }
     return root;
 }