add: 220604 [cpp]

cpp/2206/220604.cpp

@@ -0,0 +1,48 @@
+#include <vector>
+#include <string>
+#include <functional>
+
+/**
+ * 51. N-Queens
+ * 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.
+ * Given an integer n, return all distinct solutions to the n-queens puzzle. You may return the answer in any order.
+ * Each solution contains a distinct board configuration of the n-queens' placement, where 'Q' and '.' both indicate a queen and an empty space, respectively.
+ */
+
+class Solution {
+public:
+	static std::vector<std::vector<std::string>> solveNQueens(const int n) {
+		std::vector<std::vector<std::string>> ret;
+
+		bool xs[10]{}, ds[20]{}, sds[20]{}, G[10][10]{};
+		std::function<void(int)> dfs = [&](int d) {
+			if (d >= n) {
+				std::vector<std::string> ans(n);
+				for (int i = 0; i < n; ++i) {
+					std::string s(n, ' ');
+					for (int j = 0; j < n; ++j)
+						s[j] = G[i][j] ? 'Q' : '.';
+					ans[i] = s;
+				}
+				ret.push_back(ans);
+				return;
+			}
+			for (int i = 0; i < n; ++i) {
+				if (xs[i] || ds[d - i + 10] || sds[d + i])
+					continue;
+				G[d][i] = xs[i] = ds[d - i + 10] = sds[d + i] = true;
+				dfs(1 + d);
+				G[d][i] = xs[i] = ds[d - i + 10] = sds[d + i] = false;
+			}
+		};
+
+		dfs(0);
+
+		return ret;
+	}
+};
+
+int main() {
+	auto ret = Solution::solveNQueens(4);
+	return 0;
+}

cpp/2206/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2206)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2206 220602-CN.cpp)
+ADD_EXECUTABLE(2206 220604.cpp)