feat: add csharp solutions to lcof problems (doocs#826)

* 《剑指 Offer（第 2 版）》添加 C# 题解

Author: xiongbinzou

basic/sorting/BubbleSort/README.md

@@ -238,6 +238,37 @@ public class Program
 }
 ```
 
+### **Python3**
+
+```python
+def bubbleSort(arr):
+    n = len(arr)
+    # Iterate over all array elements
+    for i in range(n):
+        # Last i elements are already in place
+        for j in range(n - i - 1):
+            if arr[j] > arr[j + 1]:
+                arr[j], arr[j + 1] = arr[j + 1], arr[j]
+
+
+# 改进版本
+def bubbleSort(arr):
+    n = len(arr)
+    for i in range(n - 1):
+        has_change = False
+        for j in range(n - i - 1):
+            if arr[j] > arr[j + 1]:
+                arr[j], arr[j + 1] = arr[j + 1], arr[j]
+                has_change = True
+        if not has_change:
+            break
+
+
+arr = [64, 34, 25, 12, 22, 11, 90]
+bubbleSort(arr)
+print(arr)
+```
+
 <!-- tabs:end -->
 
 ## 算法分析

basic/sorting/InsertionSort/README.md

@@ -197,6 +197,22 @@ public class Program
 }
 ```
 
+### **Python3**
+
+```python
+def insertion_sort(array):
+    for i in range(len(array)):
+        cur_index = i
+        while array[cur_index - 1] > array[cur_index] and cur_index - 1 >= 0:
+            array[cur_index], array[cur_index - 1] = array[cur_index - 1], array[cur_index]
+            cur_index -= 1
+    return array
+
+array = [10, 17, 50, 7, 30, 24, 27, 45, 15, 5, 36, 21]
+print(insertion_sort(array))
+
+```
+
 <!-- tabs:end -->
 
 ## 算法分析

basic/sorting/SelectionSort/README.md

@@ -205,6 +205,24 @@ public class Program
 
 ```
 
+### **Python3**
+
+```python
+def selection_sort(arr):
+    n = len(arr)
+    for i in range(n-1):
+        min_index = i
+        for j in range(i+1, n):
+            if arr[j] < arr[min_index]:
+                min_index = j
+        arr[min_index], arr[i] = arr[i], arr[min_index]
+
+arr = [26, 11, 99, 33, 69, 77, 55, 56, 67]
+selection_sort(arr)
+print(arr)
+
+```
+
 <!-- tabs:end -->
 
 ## 算法分析

lcof/面试题03. 数组中重复的数字/README.md

@@ -189,6 +189,27 @@ impl Solution {
 }
 ```
 
+### **C#**
+
+```cs
+public class Solution {
+    public int FindRepeatNumber(int[] nums) {
+        int temp;
+        for (int i = 0; i < nums.Length; i++) {
+            while (i != nums[i]) {
+                if (nums[i] == nums[nums[i]]) {
+                    return nums[i];
+                }
+                temp = nums[i];
+                nums[i] = nums[temp];
+                nums[temp] = temp;
+            }
+        }
+        return -1;
+    }
+}
+```
+
 ### **...**
 
 ```

lcof/面试题03. 数组中重复的数字/Solution.cs

@@ -0,0 +1,16 @@
+public class Solution {
+    public int FindRepeatNumber(int[] nums) {
+        int temp;
+        for (int i = 0; i < nums.Length; i++) {
+            while (i != nums[i]) {
+                if (nums[i] == nums[nums[i]]) {
+                    return nums[i];
+                }
+                temp = nums[i];
+                nums[i] = nums[temp];
+                nums[temp] = temp;
+            }
+        }
+        return -1;
+    }
+}

lcof/面试题04. 二维数组中的查找/README.md

@@ -208,6 +208,29 @@ impl Solution {
 }
 ```
 
+### **C#**
+
+```cs
+public class Solution {
+    public bool FindNumberIn2DArray(int[][] matrix, int target) {
+        if (matrix.Length == 0 || matrix[0].Length == 0) {
+            return false;
+        }
+        int i = 0, j = matrix[0].Length - 1;
+        while (i < matrix.Length && j >= 0) {
+            if (target == matrix[i][j]) {
+                return true;
+            } else if (target > matrix[i][j]) {
+                i += 1;
+            } else {
+                j -= 1;
+            }
+        }
+        return false;
+    }
+}
+```
+
 ### **...**
 
 ```

lcof/面试题04. 二维数组中的查找/Solution.cs

@@ -0,0 +1,18 @@
+public class Solution {
+    public bool FindNumberIn2DArray(int[][] matrix, int target) {
+        if (matrix.Length == 0 || matrix[0].Length == 0) {
+            return false;
+        }
+        int i = 0, j = matrix[0].Length - 1;
+        while (i < matrix.Length && j >= 0) {
+            if (target == matrix[i][j]) {
+                return true;
+            } else if (target > matrix[i][j]) {
+                i += 1;
+            } else {
+                j -= 1;
+            }
+        }
+        return false;
+    }
+}

lcof/面试题05. 替换空格/README.md

@@ -183,6 +183,36 @@ impl Solution {
 }
 ```
 
+### **C#**
+
+使用 `Replace()`：
+
+```cs
+public class Solution {
+    public string ReplaceSpace(string s) {
+        return s.Replace(" ", "%20");
+    }
+}
+```
+
+遍历添加：
+
+```cs
+public class Solution {
+    public string ReplaceSpace(string s) {
+        StringBuilder res = new StringBuilder();
+        foreach (var c in s) {
+            if (c == ' ') {
+                res.Append("%20");
+            } else {
+                res.Append(c);
+            }
+        }
+        return res.ToString();
+    }
+}
+```
+
 ### **...**
 
 ```

lcof/面试题05. 替换空格/Solution.cs

@@ -0,0 +1,5 @@
+public class Solution {
+    public string ReplaceSpace(string s) {
+        return s.Replace(" ", "%20");
+    }
+}

lcof/面试题06. 从尾到头打印链表/README.md

@@ -297,6 +297,30 @@ impl Solution {
 }
 ```
 
+### **C#**
+
+```cs
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public int val;
+ *     public ListNode next;
+ *     public ListNode(int x) { val = x; }
+ * }
+ */
+ public class Solution {
+     public int[] ReversePrint(ListNode head) {
+         List<int> ans = new List<int>();
+         while (head != null) {
+             ans.Add(head.val);
+             head = head.next;
+         }
+         ans.Reverse();
+         return ans.ToArray();
+     }
+ }
+```
+
 ### **...**
 
 ```

lcof/面试题06. 从尾到头打印链表/Solution.cs

@@ -0,0 +1,19 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public int val;
+ *     public ListNode next;
+ *     public ListNode(int x) { val = x; }
+ * }
+ */
+ public class Solution {
+     public int[] ReversePrint(ListNode head) {
+         List<int> ans = new List<int>();
+         while (head != null) {
+             ans.Add(head.val);
+             head = head.next;
+         }
+         ans.Reverse();
+         return ans.ToArray();
+     }
+ }

lcof/面试题07. 重建二叉树/README.md

@@ -298,6 +298,32 @@ impl Solution {
 }
 ```
 
+### **C#**
+
+```cs
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int x) { val = x; }
+ * }
+ */
+public class Solution {
+    public TreeNode BuildTree(int[] preorder, int[] inorder) {
+        if (preorder.Length == 0) {
+            return null;
+        }
+        TreeNode root = new TreeNode(preorder[0]);
+        int idx = Array.IndexOf(inorder, root.val);
+        root.left = BuildTree(preorder[1..(index+1)], inorder[0..idx]);
+        root.right = BuildTree(preorder[(index+1)..], inorder[(idx+1)..]);
+        return root;
+    }
+}
+```
+
 ### **...**
 
 ```

lcof/面试题07. 重建二叉树/Solution.cs

@@ -0,0 +1,21 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int x) { val = x; }
+ * }
+ */
+public class Solution {
+    public TreeNode BuildTree(int[] preorder, int[] inorder) {
+        if (preorder.Length == 0) {
+            return null;
+        }
+        TreeNode root = new TreeNode(preorder[0]);
+        int idx = Array.IndexOf(inorder, root.val);
+        root.left = BuildTree(preorder[1..(index+1)], inorder[0..idx]);
+        root.right = BuildTree(preorder[(index+1)..], inorder[(idx+1)..]);
+        return root;
+    }
+}

lcof/面试题09. 用两个栈实现队列/README.md

@@ -288,10 +288,43 @@ impl CQueue {
  */
 ```
 
-### **...**
+### **C##**
+
+```cs
+public class CQueue {
+    private Stack<int> stack1;
+    private Stack<int> stack2;
+
+    public CQueue() {
+        stack1 = new Stack<int>();
+        stack2 = new Stack<int>();
+    }
+    
+    public void AppendTail(int value) {
+        stack1.Push(value);
+    }
+    
+    public int DeleteHead() {
+        if (stack2.Count == 0) {
+            while (stack1.Count != 0) {
+                stack2.Push(stack1.Pop());
+            }
+        }
+        return stack2.Count == 0 ? -1 : stack2.Pop();
+    }
+}
 
+/**
+ * Your CQueue object will be instantiated and called as such:
+ * CQueue obj = new CQueue();
+ * obj.AppendTail(value);
+ * int param_2 = obj.DeleteHead();
+ */
 ```
 
+### **...**
+
 ```
 
+```
 <!-- tabs:end -->