LeetCode-in-Go
52. N-Queens II
Hard
The n-queens puzzle is the problem of placing n queens on an n x n chessboard such that no two queens attack each other.
Given an integer n, return the number of distinct solutions to the n-queens puzzle.
Example 1:
Input: n = 4
Output: 2
Explanation: There are two distinct solutions to the 4-queens puzzle as shown.
Example 2:
Input: n = 1
Output: 1
Constraints:
1 <= n <= 9
Solution
func totalNQueens(n int) int {
row := make([]bool, n)
col := make([]bool, n)
diagonal := make([]bool, 2*n-1)
antiDiagonal := make([]bool, 2*n-1)
return totalNQueensHelper(n, 0, row, col, diagonal, antiDiagonal)
}
func totalNQueensHelper(
n, r int,
row, col, diagonal, antiDiagonal []bool,
) int {
if r == n {
return 1
}
count := 0
for c := 0; c < n; c++ {
if !row[r] && !col[c] && !diagonal[r+c] && !antiDiagonal[r-c+n-1] {
row[r], col[c], diagonal[r+c], antiDiagonal[r-c+n-1] = true, true, true, true
count += totalNQueensHelper(n, r+1, row, col, diagonal, antiDiagonal)
row[r], col[c], diagonal[r+c], antiDiagonal[r-c+n-1] = false, false, false, false
}
}
return count
}