52.N皇后Ⅱ

class Solution {
    public int totalNQueens(int n) {
        int[] nums = new int[n];
        for(int i = 0; i < n; i++){
            nums[i] = Integer.MIN_VALUE;
        }
        int[] count = new int[1];
        queen(count, nums, 0);
        return count[0];
    }

    public void queen(int[] count, int[] nums, int cur){
        if(cur == nums.length){
            count[0]++;
            return;
        }
        for(int col = 0; col < nums.length; col++){
            nums[cur] = col;
            boolean flag = true;
            for(int row = 0; row < cur; row++){
                if(nums[row] == col || Math.abs(col - nums[row]) == cur - row){
                    flag =false;
                    break;
                }
            }
            if(flag){
                queen(count, nums, cur+1);
            }
        }
    }
}