add: 220413 [cpp]

cpp/2204/220413.cpp

@@ -0,0 +1,51 @@
+#include <vector>
+#include <iostream>
+
+/**
+ * 59. Spiral Matrix II
+ * Given a positive integer n, generate an n x n matrix filled with elements from 1 to n2 in spiral order.
+ */
+
+class Solution {
+private:
+	inline static const int dX[] = {0, 1, 0, -1};
+	inline static const int dY[] = {1, 0, -1, 0};
+public:
+	static std::vector<std::vector<int>> generateMatrix(int n) {
+		int* buf = new int[n * n]{};
+		int direction = 0;
+
+		auto GetNext = [&](int& x, int& y) {
+			int nx = x + dX[direction], ny = y + dY[direction];
+			if (nx < 0 || ny < 0 || nx >= n || ny >= n || buf[nx * n + ny]) {
+				direction = (1 + direction) % 4;
+				nx = x + dX[direction], ny = y + dY[direction];
+			}
+			x = nx;
+			y = ny;
+		};
+
+		int x = 0, y = 0;
+		for (int i = 1; i <= n * n; ++i) {
+			buf[x * n + y] = i;
+			GetNext(x, y);
+		}
+
+		std::vector<std::vector<int>> ret;
+		ret.reserve(n);
+		for (int i = 0; i < n * n; i += n)
+			ret.emplace_back(buf + i, buf + i + n);
+		return ret;
+	}
+};
+
+int main() {
+	auto x = Solution::generateMatrix(4);
+	for (const auto& i : x) {
+		for (const auto& j : i) {
+			std::cout << j << ' ';
+		}
+		std::cout << '\n';
+	}
+	return 0;
+}

cpp/2204/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2204)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2204 220412.cpp)
+ADD_EXECUTABLE(2204 220413.cpp)