n queens; go implementation

52. N-Queens II/n_queens_ii.go

@@ -0,0 +1,47 @@
+package leetcode
+
+func totalNQueens(n int) int {
+	matrix := make([][]bool, n)
+	for i := range matrix {
+		matrix[i] = make([]bool, n)
+	}
+	return soln(matrix, 0)
+}
+
+func soln(matrix [][]bool, n int) int {
+	if n == len(matrix) {
+		return 1
+	}
+	count := 0
+	for i := 0; i < len(matrix); i++ {
+		if possible(matrix, n, i) {
+			matrix[n][i] = true
+			count += soln(matrix, n+1)
+			matrix[n][i] = false
+		}
+	}
+	return count
+}
+
+// 该点是否可能
+func possible(matrix [][]bool, x, y int) bool {
+	// 判断列
+	for i := x - 1; i >= 0; i-- {
+		if matrix[i][y] {
+			return false
+		}
+	}
+	// 判断左上
+	for i, j := x-1, y-1; i >= 0 && j >= 0; i, j = i-1, j-1 {
+		if matrix[i][j] {
+			return false
+		}
+	}
+	// 判断右上
+	for i, j := x-1, y+1; i >= 0 && j < len(matrix); i, j = i-1, j+1 {
+		if matrix[i][j] {
+			return false
+		}
+	}
+	return true
+}