添加 0037.解数独.md Scala版本

problems/0037.解数独.md

@@ -602,5 +602,100 @@ func solveSudoku(_ board: inout [[Character]]) {
 }
 ```
 
+### Scala
+
+详细写法：
+```scala
+object Solution {
+  
+  def solveSudoku(board: Array[Array[Char]]): Unit = {
+    backtracking(board)
+  }
+
+  def backtracking(board: Array[Array[Char]]): Boolean = {
+    for (i <- 0 until 9) {
+      for (j <- 0 until 9) {
+        if (board(i)(j) == '.') { // 必须是为 . 的数字才放数字
+          for (k <- '1' to '9') { // 这个位置放k是否合适
+            if (isVaild(i, j, k, board)) {
+              board(i)(j) = k
+              if (backtracking(board)) return true // 找到了立刻返回
+              board(i)(j) = '.' // 回溯
+            }
+          }
+          return false // 9个数都试完了，都不行就返回false
+        }
+      }
+    }
+    true // 遍历完所有的都没返回false，说明找到了
+  }
+
+  def isVaild(x: Int, y: Int, value: Char, board: Array[Array[Char]]): Boolean = {
+    // 行
+    for (i <- 0 until 9 ) {
+      if (board(i)(y) == value) {
+        return false
+      }
+    }
+    
+    // 列
+    for (j <- 0 until 9) {
+      if (board(x)(j) == value) {
+        return false
+      }
+    }
+
+    // 宫
+    var row = (x / 3) * 3
+    var col = (y / 3) * 3
+    for (i <- row until row + 3) {
+      for (j <- col until col + 3) {
+        if (board(i)(j) == value) {
+          return false
+        }
+      }
+    }
+
+    true
+  }
+}
+```
+
+遵循Scala至简原则写法：
+```scala
+object Solution {
+  
+  def solveSudoku(board: Array[Array[Char]]): Unit = {
+    backtracking(board)
+  }
+
+  def backtracking(board: Array[Array[Char]]): Boolean = {
+    // 双重for循环 + 循环守卫
+    for (i <- 0 until 9; j <- 0 until 9 if board(i)(j) == '.') {
+      // 必须是为 . 的数字才放数字，使用循环守卫判断该位置是否可以放置当前循环的数字
+      for (k <- '1' to '9' if isVaild(i, j, k, board)) { // 这个位置放k是否合适
+        board(i)(j) = k
+        if (backtracking(board)) return true // 找到了立刻返回
+        board(i)(j) = '.' // 回溯
+      }
+      return false // 9个数都试完了，都不行就返回false
+    }
+    true // 遍历完所有的都没返回false，说明找到了
+  }
+
+  def isVaild(x: Int, y: Int, value: Char, board: Array[Array[Char]]): Boolean = {
+    // 行，循环守卫进行判断
+    for (i <- 0 until 9 if board(i)(y) == value) return false
+    // 列，循环守卫进行判断
+    for (j <- 0 until 9 if board(x)(j) == value) return false
+    // 宫，循环守卫进行判断
+    var row = (x / 3) * 3
+    var col = (y / 3) * 3
+    for (i <- row until row + 3; j <- col until col + 3 if board(i)(j) == value) return false
+    true // 最终没有返回false，就说明该位置可以填写true
+  }
+}
+```
+
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