Merge pull request #1202 from xiaofei-2020/back21

添加（0037.解数独.md）：增加typescript版本

problems/0037.解数独.md

@@ -439,6 +439,55 @@ var solveSudoku = function(board) {
 };
 ```
 
+### TypeScript
+
+```typescript
+/**
+ Do not return anything, modify board in-place instead.
+ */
+function isValid(col: number, row: number, val: string, board: string[][]): boolean {
+    let n: number = board.length;
+    // 列向检查
+    for (let rowIndex = 0; rowIndex < n; rowIndex++) {
+        if (board[rowIndex][col] === val) return false;
+    }
+    // 横向检查
+    for (let colIndex = 0; colIndex < n; colIndex++) {
+        if (board[row][colIndex] === val) return false;
+    }
+    // 九宫格检查
+    const startX = Math.floor(col / 3) * 3;
+    const startY = Math.floor(row / 3) * 3;
+    for (let rowIndex = startY; rowIndex < startY + 3; rowIndex++) {
+        for (let colIndex = startX; colIndex < startX + 3; colIndex++) {
+            if (board[rowIndex][colIndex] === val) return false;
+        }
+    }
+    return true;
+}
+function solveSudoku(board: string[][]): void {
+    let n: number = 9;
+    backTracking(n, board);
+    function backTracking(n: number, board: string[][]): boolean {
+        for (let row = 0; row < n; row++) {
+            for (let col = 0; col < n; col++) {
+                if (board[row][col] === '.') {
+                    for (let i = 1; i <= n; i++) {
+                        if (isValid(col, row, String(i), board)) {
+                            board[row][col] = String(i);
+                            if (backTracking(n, board) === true) return true;
+                            board[row][col] = '.';
+                        }
+                    }
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+};
+```
+
 ### C 
 
 ```C