Merge branch 'master' of github.com:krahets/hello-algo

codes/c/chapter_array_and_linkedlist/array.c

@@ -0,0 +1,112 @@
+/*
+ * File: array.c
+ * Created Time: 2022-12-20
+ * Author: MolDuM (moldum@163.com)
+ */
+
+#include "../include/include.h"
+
+/* 随机返回一个数组元素 */
+int randomAccess(int* nums, int size) {
+    // 在区间 [0, size) 中随机抽取一个数字
+    int randomIndex = rand() % size;
+    // 获取并返回随机元素
+    int randomNum = nums[randomIndex];
+    return randomNum;
+}
+
+/* 扩展数组长度 */
+int* extend(int* nums, int size, int enlarge) {
+    // 初始化一个扩展长度后的数组
+    int* res = (int *)malloc(sizeof(int) * (size + enlarge));
+    // 将原数组中的所有元素复制到新数组
+    for (int i = 0; i < size; i++) {
+        res[i] = nums[i];
+    }
+    // 初始化扩展后的空间
+    for (int i = size; i < size + enlarge; i++) {
+        res[i] = 0;
+    }
+    // 返回扩展后的新数组
+    return res;
+}
+
+/* 在数组的索引 index 处插入元素 num */
+void insert(int* nums, int size, int num, int index) {
+    // 把索引 index 以及之后的所有元素向后移动一位
+    for (int i = size - 1; i > index; i--) {
+        nums[i] = nums[i - 1];
+    }
+    // 将 num 赋给 index 处元素
+    nums[index] = num;
+}
+
+/* 删除索引 index 处元素 */
+void removeItem(int* nums, int size, int index) {
+    // 把索引 index 之后的所有元素向前移动一位
+    for (int i = index; i < size - 1; i++) {
+        nums[i] = nums[i + 1];
+    }
+}
+
+/* 遍历数组 */
+void traverse(int* nums, int size) {
+    int count = 0;
+    // 通过索引遍历数组
+    for (int i = 0; i < size; i++) {
+        count++;
+    }
+}
+
+/* 在数组中查找指定元素 */
+int find(int* nums, int size, int target) {
+    for (int i = 0; i < size; i++) {
+        if (nums[i] == target)
+            return i;
+    }
+    return -1;
+}
+
+
+/* Driver Code */
+int main() {
+    /* 初始化数组 */
+    int size = 5;
+    int arr[5];
+    printf("数组 arr = ");
+    printArray(arr, size);
+
+    int nums[5] = { 1, 3, 2, 5, 4 };
+    printf("数组 nums = ");
+    printArray(nums, size);
+    
+    /* 随机访问 */
+    int randomNum = randomAccess(nums, size);
+    printf("在 nums 中获取随机元素 %d", randomNum);
+    
+    /* 长度扩展 */
+    int enlarge = 3;
+    int* res = extend(nums, size, enlarge);
+    size += enlarge;
+    printf("将数组长度扩展至 8 ，得到 nums = ");
+    printArray(res, size);
+    
+    /* 插入元素 */
+    insert(res, size, 6, 3);
+    printf("在索引 3 处插入数字 6 ，得到 nums = ");
+    printArray(res, size);
+
+    /* 删除元素 */
+    removeItem(res, size, 2);
+    printf("删除索引 2 处的元素，得到 nums = ");
+    printArray(res, size);
+    
+    /* 遍历数组 */
+    traverse(res, size);
+    
+    /* 查找元素 */
+    int index = find(res, size, 3);
+    printf("在 res 中查找元素 3 ，得到索引 = %d\n", index);
+
+    return 0;
+}

codes/c/include/PrintUtil.h

@@ -0,0 +1,30 @@
+/*
+ * File: PrintUtil.h
+ * Created Time: 2022-12-21
+ * Author: MolDum (moldum@163.com)
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+// #include "ListNode.h"
+// #include "TreeNode.h"
+
+/**
+ * @brief Print an Array
+ * 
+ * @param arr 
+ * @param n 
+ */
+
+static void printArray(int* arr, int n)
+{
+    printf("[");
+    for (int i = 0; i < n - 1; i++) {
+        printf("%d, ", arr[i]);
+    }
+    printf("%d]\n", arr[n-1]);
+}
+
+

codes/c/include/include.h

@@ -1,2 +1,12 @@
+/*
+ * File: include.h
+ * Created Time: 2022-12-20
+ * Author: MolDuM (moldum@163.com)
+ */
+
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 #include <stdbool.h>
+
+#include "PrintUtil.h"

codes/swift/Package.swift

@@ -8,11 +8,13 @@ let package = Package(
         .executable(name: "time_complexity", targets: ["time_complexity"]),
         .executable(name: "worst_best_time_complexity", targets: ["worst_best_time_complexity"]),
         .executable(name: "space_complexity", targets: ["space_complexity"]),
+        .executable(name: "leetcode_two_sum", targets: ["leetcode_two_sum"]),
     ],
     targets: [
         .target(name: "utils", path: "utils"),
         .executableTarget(name: "time_complexity", path: "chapter_computational_complexity", sources: ["time_complexity.swift"]),
         .executableTarget(name: "worst_best_time_complexity", path: "chapter_computational_complexity", sources: ["worst_best_time_complexity.swift"]),
         .executableTarget(name: "space_complexity", dependencies: ["utils"], path: "chapter_computational_complexity", sources: ["space_complexity.swift"]),
+        .executableTarget(name: "leetcode_two_sum", path: "chapter_computational_complexity", sources: ["leetcode_two_sum.swift"]),
     ]
 )

codes/swift/chapter_computational_complexity/leetcode_two_sum.swift

@@ -0,0 +1,46 @@
+/*
+ * File: leetcode_two_sum.swift
+ * Created Time: 2023-01-03
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+func twoSumBruteForce(nums: [Int], target: Int) -> [Int] {
+    // 两层循环，时间复杂度 O(n^2)
+    for i in nums.indices.dropLast() {
+        for j in nums.indices.dropFirst(i + 1) {
+            if nums[i] + nums[j] == target {
+                return [i, j]
+            }
+        }
+    }
+    return [0]
+}
+
+func twoSumHashTable(nums: [Int], target: Int) -> [Int] {
+    // 辅助哈希表，空间复杂度 O(n)
+    var dic: [Int: Int] = [:]
+    // 单层循环，时间复杂度 O(n)
+    for i in nums.indices {
+        if let j = dic[target - nums[i]] {
+            return [j, i]
+        }
+        dic[nums[i]] = i
+    }
+    return [0]
+}
+
+@main
+enum LeetcodeTwoSum {
+    static func main() {
+        // ======= Test Case =======
+        let nums = [2, 7, 11, 15]
+        let target = 9
+        // ====== Driver Code ======
+        // 方法一
+        var res = twoSumBruteForce(nums: nums, target: target)
+        print("方法一 res = \(res)")
+        // 方法二
+        res = twoSumHashTable(nums: nums, target: target)
+        print("方法二 res = \(res)")
+    }
+}

docs/chapter_computational_complexity/space_time_tradeoff.md

@@ -149,6 +149,22 @@ comments: true
     }
     ```
 
+=== "Swift"
+
+    ```swift title="leetcode_two_sum.swift"
+    func twoSumBruteForce(nums: [Int], target: Int) -> [Int] {
+        // 两层循环，时间复杂度 O(n^2)
+        for i in nums.indices.dropLast() {
+            for j in nums.indices.dropFirst(i + 1) {
+                if nums[i] + nums[j] == target {
+                    return [i, j]
+                }
+            }
+        }
+        return [0]
+    }
+    ```
+
 ### 方法二：辅助哈希表
 
 时间复杂度 $O(N)$ ，空间复杂度 $O(N)$ ，属于「空间换时间」。
@@ -294,3 +310,20 @@ comments: true
         }
     }
     ```
+
+=== "Swift"
+
+    ```swift title="leetcode_two_sum.swift"
+    func twoSumHashTable(nums: [Int], target: Int) -> [Int] {
+        // 辅助哈希表，空间复杂度 O(n)
+        var dic: [Int: Int] = [:]
+        // 单层循环，时间复杂度 O(n)
+        for i in nums.indices {
+            if let j = dic[target - nums[i]] {
+                return [j, i]
+            }
+            dic[nums[i]] = i
+        }
+        return [0]
+    }
+    ```

docs/chapter_tree/binary_tree.md

@@ -120,7 +120,7 @@ comments: true
 
 - 「根结点 Root Node」：二叉树最顶层的结点，其没有父结点；
 - 「叶结点 Leaf Node」：没有子结点的结点，其两个指针都指向 $\text{null}$ ；
-- 结点所处「层 Level」：从顶置底依次增加，根结点所处层为 1 ；
+- 结点所处「层 Level」：从顶至底依次增加，根结点所处层为 1 ；
 - 结点「度 Degree」：结点的子结点数量。二叉树中，度的范围是 0, 1, 2 ；
 - 「边 Edge」：连接两个结点的边，即结点指针；
 - 二叉树「高度」：二叉树中根结点到最远叶结点走过边的数量；