add: 220226 [cpp]

cpp/2202/220226.cpp

@@ -0,0 +1,101 @@
+#include <queue>
+#include <vector>
+#include <cstring>
+#include <iostream>
+#include <functional>
+
+/**
+ * 847. Shortest Path Visiting All Nodes
+ * You have an undirected, connected graph of n nodes labeled from 0 to n - 1. You are given an array graph where graph[i] is a list of all the nodes connected with node i by an edge.
+ * Return the length of the shortest path that visits every node. You may start and stop at any node, you may revisit nodes multiple times, and you may reuse edges.
+ */
+
+class Solution {
+private:
+	static void bfs(const std::vector<std::vector<int>>& G, int begin, int* ret) {
+		int n = G.size();
+
+		// Insert: (node#, length)
+		std::queue<int> q;
+		bool* const vis = new bool[n]{};
+		q.push(begin);
+		q.push(0);
+		vis[begin] = true;
+
+		while (!q.empty()) {
+			int idx = q.front();
+			q.pop();
+			int len = q.front();
+			q.pop();
+
+			ret[idx] = len;
+
+			for (int i : G[idx]) {
+				if (!vis[i]) {
+					q.push(i);
+					q.push(1 + len);
+					vis[i] = true;
+				}
+			}
+		}
+
+		delete[] vis;
+	}
+
+	static inline constexpr int bitSetAdd(int set, int id) {
+		return set | (1 << id);
+	}
+
+	static inline constexpr int bitSetRemove(int set, int id) {
+		return set & (~(1 << id));
+	}
+
+public:
+	static int shortestPathLength(const std::vector<std::vector<int>>& graph) {
+		int n = graph.size();
+		int lens[n][n];
+		for (int i = 0; i < n; ++i) {
+			bfs(graph, i, lens[i]);
+		}
+
+		// dp: let dp[visitedSet][node] be the remaining length to
+		// reach the all-node-visited state.
+		// dp[(1 << n) - 1][x] always be 0;
+		int dp[1 << n][n];
+		std::memset(dp, -1, sizeof dp);
+		std::memset(dp[(1 << n) - 1], 0, sizeof dp[(1 << n) - 1]);
+
+		// visited includes node.
+		std::function<int(int, int)> calc;
+		calc = [&](int visited, int node) {
+			if (dp[visited][node] != -1)
+				return dp[visited][node];
+
+			int& now = dp[visited][node];
+			now = 0x7FFFFFFF;
+			// Try goes to next node
+			for (int i = 0; i < n; ++i) {
+				if (!(visited & (1 << i))) {
+					// This node not visited, goes to it
+					// directly regardless of nodes not
+					// visited along the way
+					now = std::min(now, lens[node][i] + calc(bitSetAdd(visited, i), i));
+				}
+			}
+
+			return now;
+		};
+
+		int ret = 0x7FFFFFFF;
+		for (int i = 0; i < n; ++i) {
+			ret = std::min(ret, calc(bitSetAdd(0, i), i));
+		}
+
+		return ret;
+	}
+};
+
+int main() {
+	std::cout << Solution::shortestPathLength({{1},{0,2,4},{1,3,4},{2},{1,2}});
+	return 0;
+}

cpp/2202/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2202)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2202 220226-CN.cpp)
+ADD_EXECUTABLE(2202 220226.cpp)