add: 230407

cpp/2304/230407.cpp

@@ -0,0 +1,58 @@
+#include <iostream>
+#include <queue>
+#include <utility>
+#include <vector>
+#include <numeric>
+
+/**
+ * 1020. Number of Enclaves
+ *
+ * You are given an m x n binary matrix grid, where 0 represents a sea cell and 1 represents a land cell.
+ * A move consists of walking from one land cell to another adjacent (4-directionally) land cell or walking off the boundary of the grid.
+ * Return the number of land cells in grid for which we cannot walk off the boundary of the grid in any number of moves.
+ */
+
+class Solution {
+private:
+	static const inline int dX[] = {0, 1, 0, -1}, dY[] = {1, 0, -1, 0};
+public:
+	static int numEnclaves(std::vector<std::vector<int>>&);
+};
+
+int Solution::numEnclaves(std::vector<std::vector<int>>& G) {
+	const int m = G.size(), n = G.front().size();
+	auto setAs0 = [&](int x, int y) {
+		if (G[x][y] == 0) return 0;
+		std::queue<std::pair<int, int>> q;
+		q.emplace(x, y);
+		int ret = 0;
+		std::vector<bool> vis(m * n);
+		for (int nx, ny; !q.empty(); q.pop()) {
+			auto&& [cx, cy] = q.front();
+			G[cx][cy] = 0;
+			++ret;
+			for (int i = 0; i < 4; ++i) {
+				nx = cx + dX[i];
+				ny = cy + dY[i];
+				if (nx >= 0 && nx < m && ny >= 0 && ny < n && G[nx][ny] != 0 && !vis[nx * n + ny]) {
+					q.emplace(nx, ny);
+					vis[nx * n + ny] = true;
+				}
+			}
+		}
+		return ret;
+	};
+	for (int i = 0; i < n; ++i)
+		setAs0(0, i), setAs0(m - 1, i);
+	for (int i = 1; i < m - 1; ++i)
+		setAs0(i, 0), setAs0(i, n - 1);
+	return std::transform_reduce(G.begin(), G.end(), 0, [](int x, int y){ return x + y; }, [](auto&& x) {
+		return std::reduce(x.begin(), x.end(), 0);
+	});
+}
+
+int main() {
+	std::vector<std::vector<int>> a {{0,0,0,0},{1,0,1,0},{0,1,1,0},{0,0,0,0}};
+	std::cout << Solution::numEnclaves(a);
+	return 0;
+}

cpp/2304/CMakeLists.txt

@@ -4,4 +4,4 @@ PROJECT(2304)
 SET(CMAKE_CXX_STANDARD 23)
 SET(CMAKE_EXPORT_COMPILE_COMMANDS true)
 
-ADD_EXECUTABLE(2304 230406.cpp)
+ADD_EXECUTABLE(2304 230407.cpp)