Merge pull request #2377 from eeee0717/master

Update 0047.全排列2，添加C#

Author: youngyangyang04

problems/0037.解数独.md

@@ -756,6 +756,59 @@ object Solution {
   }
 }
 ```
+### C#
+```csharp
+public class Solution
+{
+    public void SolveSudoku(char[][] board)
+    {
+        BackTracking(board);
+    }
+    public bool BackTracking(char[][] board)
+    {
+        for (int i = 0; i < board.Length; i++)
+        {
+            for (int j = 0; j < board[0].Length; j++)
+            {
+                if (board[i][j] != '.') continue;
+                for (char k = '1'; k <= '9'; k++)
+                {
+                    if (IsValid(board, i, j, k))
+                    {
+                        board[i][j] = k;
+                        if (BackTracking(board)) return true;
+                        board[i][j] = '.';
+                    }
+                }
+                return false;
+            }
+
+        }
+        return true;
+    }
+    public bool IsValid(char[][] board, int row, int col, char val)
+    {
+        for (int i = 0; i < 9; i++)
+        {
+            if (board[i][col] == val) return false;
+        }
+        for (int i = 0; i < 9; i++)
+        {
+            if (board[row][i] == val) return false;
+        }
+        int startRow = (row / 3) * 3;
+        int startCol = (col / 3) * 3;
+        for (int i = startRow; i < startRow + 3; i++)
+        {
+            for (int j = startCol; j < startCol + 3; j++)
+            {
+                if (board[i][j] == val) return false;
+            }
+        }
+        return true;
+    }
+}
+```
 
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problems/0047.全排列II.md

@@ -521,6 +521,38 @@ object Solution {
   }
 }
 ```
+### C#
+```csharp
+public class Solution
+{
+    public List<IList<int>> res = new List<IList<int>>();
+    public List<int> path = new List<int>();
+    public IList<IList<int>> PermuteUnique(int[] nums)
+    {
+        Array.Sort(nums);
+        BackTracking(nums, new bool[nums.Length]);
+        return res;
+    }
+    public void BackTracking(int[] nums, bool[] used)
+    {
+        if (nums.Length == path.Count)
+        {
+            res.Add(new List<int>(path));
+            return;
+        }
+        for (int i = 0; i < nums.Length; i++)
+        {
+            if (i > 0 && nums[i] == nums[i - 1] && used[i - 1] == false) continue;
+            if (used[i]) continue;
+            path.Add(nums[i]);
+            used[i] = true;
+            BackTracking(nums, used);
+            path.RemoveAt(path.Count - 1);
+            used[i] = false;
+        }
+    }
+}
+```
 
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problems/0051.N皇后.md

@@ -865,6 +865,60 @@ object Solution {
   }
 }
 ```
+### C#
+```csharp
+public class Solution
+{
+    public List<IList<string>> res = new();
+    public IList<IList<string>> SolveNQueens(int n)
+    {
+        char[][] chessBoard = new char[n][];
+        for (int i = 0; i < n; i++)
+        {
+            chessBoard[i] = new char[n];
+            for (int j = 0; j < n; j++)
+            {
+                chessBoard[i][j] = '.';
+            }
+        }
+        BackTracking(n, 0, chessBoard);
+        return res;
+    }
+    public void BackTracking(int n, int row, char[][] chessBoard)
+    {
+        if (row == n)
+        {
+            res.Add(chessBoard.Select(x => new string(x)).ToList());
+            return;
+        }
+        for (int col = 0; col < n; col++)
+        {
+            if (IsValid(row, col, chessBoard, n))
+            {
+                chessBoard[row][col] = 'Q';
+                BackTracking(n, row + 1, chessBoard);
+                chessBoard[row][col] = '.';
+            }
+        }
+    }
+    public bool IsValid(int row, int col, char[][] chessBoard, int n)
+    {
+        for (int i = 0; i < row; i++)
+        {
+            if (chessBoard[i][col] == 'Q') return false;
+        }
+        for (int i = row - 1, j = col - 1; i >= 0 && j >= 0; i--, j--)
+        {
+            if (chessBoard[i][j] == 'Q') return false;
+        }
+        for (int i = row - 1, j = col + 1; i >= 0 && j < n; i--, j++)
+        {
+            if (chessBoard[i][j] == 'Q') return false;
+        }
+        return true;
+    }
+}
+```
 
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problems/0053.最大子序和.md

@@ -406,6 +406,26 @@ object Solution {
   }
 }
 ```
+### C#
+**贪心**
+```csharp
+public class Solution
+{
+    public int MaxSubArray(int[] nums)
+    {
+        int res = Int32.MinValue;
+        int count = 0;
+        for (int i = 0; i < nums.Length; i++)
+        {
+            count += nums[i];
+            res = Math.Max(res, count);
+            if (count < 0) count = 0;
+        }
+        return res;
+    }
+}
+```
+
 
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problems/0376.摆动序列.md

@@ -64,7 +64,7 @@
 
 在计算是否有峰值的时候，大家知道遍历的下标 i ，计算 prediff（nums[i] - nums[i-1]） 和 curdiff（nums[i+1] - nums[i]），如果`prediff < 0 && curdiff > 0` 或者 `prediff > 0 && curdiff < 0` 此时就有波动就需要统计。
 
-这是我们思考本题的一个大题思路，但本题要考虑三种情况：
+这是我们思考本题的一个大体思路，但本题要考虑三种情况：
 
 1. 情况一：上下坡中有平坡
 2. 情况二：数组首尾两端
@@ -692,6 +692,27 @@ object Solution {
   }
 }
 ```
+### C#
+```csharp
+public class Solution
+{
+    public int WiggleMaxLength(int[] nums)
+    {
+        if (nums.Length < 2) return nums.Length;
+        int curDiff = 0, preDiff = 0, res = 1;
+        for (int i = 0; i < nums.Length - 1; i++)
+        {
+            curDiff = nums[i + 1] - nums[i];
+            if ((curDiff > 0 && preDiff <= 0) || (curDiff < 0 && preDiff >= 0))
+            {
+                res++;
+                preDiff = curDiff;
+            }
+        }
+        return res;
+    }
+}
+```
 
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problems/0455.分发饼干.md

@@ -378,6 +378,28 @@ object Solution {
   }
 }
 ```
+### C#
+```csharp
+public class Solution
+{
+    public int FindContentChildren(int[] g, int[] s)
+    {
+        Array.Sort(g);
+        Array.Sort(s);
+        int index = s.Length - 1;
+        int res = 0;
+        for (int i = g.Length - 1; i >=0; i--)
+        {
+            if(index >=0 && s[index]>=g[i])
+            {
+                res++;
+                index--;
+            }
+        }
+        return res;
+    }
+}
+```
 
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