add: 220430 [cpp]

cpp/2204/220430.cpp

@@ -0,0 +1,92 @@
+#include <string>
+#include <vector>
+#include <queue>
+#include <unordered_map>
+#include <iostream>
+
+/**
+ * 399. Evaluate Division
+ * You are given an array of variable pairs equations and an array of real numbers values, where equations[i] = [Ai, Bi] and values[i] represent the equation Ai / Bi = values[i]. Each Ai or Bi is a string that represents a single variable.
+ * You are also given some queries, where queries[j] = [Cj, Dj] represents the jth query where you must find the answer for Cj / Dj = ?.
+ * Return the answers to all queries. If a single answer cannot be determined, return -1.0.
+ */
+
+class Solution {
+public:
+	static std::vector<double> calcEquation(const std::vector<std::vector<std::string>>& equations, const std::vector<double>& values, const std::vector<std::vector<std::string>>& queries) {
+		int nodeCnt = 0;
+		std::unordered_map<std::string, int> strId;
+
+		// Give strings IDs
+		const int n = equations.size();
+		for (int i = 0; i < n; ++i) {
+			// Place them into map, if not present
+			if (!strId.count(equations[i][0]))
+				strId[equations[i][0]] = nodeCnt++;
+			if (!strId.count(equations[i][1]))
+				strId[equations[i][1]] = nodeCnt++;
+		}
+
+		std::vector<std::unordered_map<int, double>> G(nodeCnt);
+		// Process equations
+		for (int i = 0; i < n; ++i) {
+			const int fId = strId[equations[i][0]], tId = strId[equations[i][1]];
+			const double val = values[i];
+			G[tId][fId] = 1.0 / (G[fId][tId] = val);
+		}
+
+		auto getVal = [&](int fromId, int toId) {
+			std::queue<std::pair<int, double>> q;
+
+			q.push({fromId, 1.0});
+			std::vector<bool> vis(nodeCnt);
+			vis[fromId] = true;
+			while (!q.empty()) {
+				const auto [node, val] = q.front();
+				q.pop();
+
+				for (const auto& [t, v] : G[node]) {
+					auto nextVal = val * v;
+					if (t == toId)
+						return nextVal;
+					if (vis[t])
+						continue;
+					vis[t] = true;
+
+					// Cache edge for future use
+					G[fromId][t] = nextVal;
+					G[t][fromId] = 1.0 / nextVal;
+
+					// Push into BFS queue
+					q.push({t, nextVal});
+				}
+			}
+
+			// Not found everywhere
+			return -1.0;
+		};
+
+		std::vector<double> ret;
+		// Process queries
+		// current ID, current val
+		for (const auto& query : queries) {
+			const auto& from = query[0];
+			const auto& to = query[1];
+
+			if (!strId.count(from) || !strId.count(to))
+				ret.push_back(-1.0);
+			else if (from == to)
+				ret.push_back(1.0);
+			else
+				ret.push_back(getVal(strId[from], strId[to]));
+		}
+		return ret;
+	}
+};
+
+int main() {
+	auto ans = Solution::calcEquation({{"a","b"},{"b","c"},{"bc","cd"}}, {1.5,2.5,5.0}, {{"a","c"},{"c","b"},{"bc","cd"},{"cd","bc"}});
+	for (auto x : ans)
+		std::cout << x << std::endl;
+	return 0;
+}

cpp/2204/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2204)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2204 220429-CN.cpp)
+ADD_EXECUTABLE(2204 220430.cpp)