题目：

题解：

func totalNQueens(n int) (ans int) {columns := make([]bool, n)        // 列上是否有皇后diagonals1 := make([]bool, 2*n-1) // 左上到右下是否有皇后diagonals2 := make([]bool, 2*n-1) // 右上到左下是否有皇后var backtrack func(int)backtrack = func(row int) {if row == n {ans++return}for col, hasQueen := range columns {d1, d2 := row+n-1-col, row+colif hasQueen || diagonals1[d1] || diagonals2[d2] {continue}columns[col] = truediagonals1[d1] = truediagonals2[d2] = truebacktrack(row + 1)columns[col] = falsediagonals1[d1] = falsediagonals2[d2] = false}}backtrack(0)return
}