49 lines
1.3 KiB
C++
49 lines
1.3 KiB
C++
#include <vector>
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#include <string>
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#include <functional>
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/**
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* 51. N-Queens
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* 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.
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* Given an integer n, return all distinct solutions to the n-queens puzzle. You may return the answer in any order.
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* Each solution contains a distinct board configuration of the n-queens' placement, where 'Q' and '.' both indicate a queen and an empty space, respectively.
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*/
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class Solution {
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public:
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static std::vector<std::vector<std::string>> solveNQueens(const int n) {
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std::vector<std::vector<std::string>> ret;
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bool xs[10]{}, ds[20]{}, sds[20]{}, G[10][10]{};
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std::function<void(int)> dfs = [&](int d) {
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if (d >= n) {
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std::vector<std::string> ans(n);
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for (int i = 0; i < n; ++i) {
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std::string s(n, ' ');
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for (int j = 0; j < n; ++j)
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s[j] = G[i][j] ? 'Q' : '.';
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ans[i] = s;
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}
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ret.push_back(ans);
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return;
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}
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for (int i = 0; i < n; ++i) {
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if (xs[i] || ds[d - i + 10] || sds[d + i])
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continue;
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G[d][i] = xs[i] = ds[d - i + 10] = sds[d + i] = true;
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dfs(1 + d);
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G[d][i] = xs[i] = ds[d - i + 10] = sds[d + i] = false;
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}
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};
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dfs(0);
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return ret;
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}
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};
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int main() {
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auto ret = Solution::solveNQueens(4);
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return 0;
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}
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