add: 220605 + CN

cpp/2206/220605-CN.cpp

@@ -0,0 +1,19 @@
+#include <vector>
+#include <ctime>
+#include <random>
+
+class Solution {
+private:
+	double radius, x_center, y_center;
+	std::mt19937_64 r;
+
+public:
+	Solution(double radius, double xCenter, double yCenter) : radius(radius), x_center(xCenter), y_center(yCenter) {
+		r = std::mt19937_64(std::time(nullptr));
+	}
+
+	std::vector<double> randPoint() {
+		double l = double (r()) / std::mt19937_64::max() * radius, d = double (r()) / std::mt19937_64::max() * std::acos(-1.0);
+		return {x_center + std::sin(d) * l, y_center + std::cos(d) * l};
+	}
+};

cpp/2206/220605.cpp

@@ -0,0 +1,38 @@
+#include <functional>
+
+/**
+ * 52. N-Queens II
+ * 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 the number of distinct solutions to the n-queens puzzle.
+ */
+
+class Solution {
+public:
+	static int totalNQueens(int n) {
+		int ret = 0;
+
+		bool xs[10]{}, ds[20]{}, sds[20]{}, G[10][10]{};
+		std::function<void(int)> dfs = [&](int d) {
+			if (d >= n) {
+				++ret;
+				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::totalNQueens(4);
+	return 0;
+}

cpp/2206/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2206)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2206 220604.cpp)
+ADD_EXECUTABLE(2206 220605-CN.cpp)