[leetcode] N-Queens II

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Follow up for N-Queens problem.

Now, instead outputting board configurations, return the total number of distinct solutions.

https://oj.leetcode.com/problems/n-queens-ii/

思路：參考N-Queens，只統計個數即可。

 

public class Solution {public int totalNQueens(int n) {if (n <= 0)return 0;int[] perm = new int[n];slove(perm, 0, n);return count;}private int count = 0;private void slove(int[] perm, int cur, int n) {if (cur == n) {count++;} else {int i;for (i = 0; i < n; i++) {int j;boolean ok = true;for (j = 0; j < cur; j++) {if (perm[j] == i || perm[j] - j == i - cur|| perm[j] + j == i + cur)ok = false;}if (ok) {perm[cur] = i;slove(perm, cur + 1, n);}}}}public static void main(String[] args) {System.out.println(new Solution().totalNQueens(8));}}