adding Problem 37

按照网上的算法，编写了一个答案，但是不能通过单元测试。

Author: aQua

Algorithms/0037.sudoku-solver/sudoku-solver.go

@@ -1,21 +1,62 @@
 package Problem0037
 
 func solveSudoku(board [][]byte) {
-	res := [][]byte{
-		[]byte("519748632"),
-		[]byte("783652419"),
-		[]byte("426139875"),
-		[]byte("357986241"),
-		[]byte("264317598"),
-		[]byte("198524367"),
-		[]byte("975863124"),
-		[]byte("832491756"),
-		[]byte("641275983"),
+	nums := []byte("519783426")
+	for _, n := range nums {
+		if !fillBlock(board, n, 0) {
+			panic("此题无解")
+		}
+	}
+}
+
+func fillBlock(board [][]byte, n byte, block int) bool {
+	print(board, n, block)
+
+	if block == 9 {
+		return true
+	}
+
+	rowZero := (block / 3) * 3
+	colZero := (block % 3) * 3
+
+	// 检查block中，是否已经存在 b 了
+	had := func() bool {
+		for r := rowZero; r < rowZero+3; r++ {
+			for c := colZero; c < colZero+3; c++ {
+				if board[r][c] == n {
+					return true
+				}
+			}
+		}
+		return false
 	}
 
-	for i, v := range board {
-		for j := range v {
-			board[i][j] = res[i][j]
+	if had() {
+		return fillBlock(board, n, block+1)
+	}
+	// 检查(r,c)所在的行和列是否已经存在 b 了
+	isClear := func(r, c int) bool {
+		for i := 0; i < 9; i++ {
+			if board[r][i] == n || board[i][c] == n {
+				return false
+			}
 		}
+		return true
 	}
+
+	for r := rowZero; r < rowZero+3; r++ {
+		for c := colZero; c < colZero+3; c++ {
+			if board[r][c] == '.' && isClear(r, c) {
+				board[r][c] = n
+				if fillBlock(board, n, block+1) {
+					return true
+				}
+				// 后面的填写不成功，所以需要还原这个格子
+				board[r][c] = '.'
+				print(board, n, block)
+			}
+		}
+	}
+
+	return false
 }

Algorithms/0037.sudoku-solver/sudoku-solver_test.go

@@ -64,3 +64,14 @@ func Test_Problem0036(t *testing.T) {
 		ast.Equal(a.one, p.one, "输入:%v", p)
 	}
 }
+
+func print(board [][]byte, b byte, block int) {
+	fmt.Printf("\n====fill %d in block %d ====", b-'0', block)
+
+	for i := range board {
+		if i%3 == 0 {
+			fmt.Println()
+		}
+		fmt.Println(string(board[i][0:3]), " ", string(board[i][3:6]), " ", string(board[i][6:]))
+	}
+}