add: 230324

cpp/2303/230324.cpp

@@ -0,0 +1,45 @@
+#include <vector>
+#include <unordered_set>
+#include <algorithm>
+#include <functional>
+#include <iostream>
+
+/**
+ * 1466. Reorder Routes to Make All Paths Lead to the City Zero
+ *
+ * There are n cities numbered from 0 to n - 1 and n - 1 roads such that there is only one way to travel between two different cities (this network form a tree). Last year, The ministry of transport decided to orient the roads in one direction because they are too narrow.
+ * Roads are represented by connections where connections[i] = [ai, bi] represents a road from city ai to city bi.
+ * This year, there will be a big event in the capital (city 0), and many people want to travel to this city.
+ * Your task consists of reorienting some roads such that each city can visit the city 0. Return the minimum number of edges changed.
+ * It's guaranteed that each city can reach city 0 after reorder.
+ */
+
+class Solution {
+public:
+	static int minReorder(int n, const std::vector<std::vector<int>>& connections) {
+		std::vector<std::unordered_set<int>> vs(n);
+		for (const auto& i : connections) {
+			vs[i[0]].insert(-i[1]);
+			vs[i[1]].insert(i[0]);
+		}
+		std::vector<bool> vis(n);
+		std::function<int(int)> dfs = [&](int cur) {
+			vis[cur] = true;
+			int ret = 0;
+			for (int nx : vs[cur]) {
+				if (vis[std::abs(nx)])
+					continue;
+				ret += (nx < 0) + dfs(std::abs(nx));
+			}
+			return ret;
+		};
+		return dfs(0);
+	}
+};
+
+int main() {
+	std::cout << Solution::minReorder(6, {
+		{0, 1}, {1, 3}, {2, 3}, {4, 0}, {4, 5}
+	});
+	return 0;
+}

cpp/2303/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2303)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2303 230324-CN.cpp)
+ADD_EXECUTABLE(2303 230324.cpp)