LeetCode51 n-皇后

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字数统计: 228 | 阅读时长 ≈ 1

链接：https://leetcode-cn.com/problems/n-queens/description/

题面

经典的N皇后问题，要求所有皇后互相不冲突的解法

解法

经典的回溯解法
学习一下对角线的标记方法，之前学过可能忘记了
重温一下

代码

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class Solution {
public:
    vector<vector<string>> boards;
    void backtrack(vector<string>& cur, vector<bool>& col, vector<bool>& ld, vector<bool>& rd, int pos, int n) {
        if (pos == n) {
            boards.push_back(cur);
            return;
        }
        for (int i = 0; i < n; i++) {
            if (col[i] || rd[pos + i] || ld[n + pos - i]) {
                continue;
            }
            col[i] = rd[pos + i] = ld[n + pos - i] = 1;
            cur[pos][i] = 'Q';
            backtrack(cur, col, ld, rd, pos + 1, n);
            cur[pos][i] = '.';
            col[i] = rd[pos + i] = ld[n + pos - i] = 0;
        }
    }
    vector<vector<string>> solveNQueens(int n) {
        vector<string> currBoard(n, string(n, '.'));
        vector<bool> col(n, false), ld(2 * n + 1, false), rd(2 * n + 1, false);
        backtrack(currBoard, col, ld, rd, 0, n);
        return boards;
    }
};