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除法求值⚓︎

Leetcode题目链接

描述⚓︎

详见中文题目链接。

解答⚓︎

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class Solution {
public:
    vector<double> calcEquation(vector<vector<string>>& equations, vector<double>& values, vector<vector<string>>& queries) {
        unordered_set<string> vertices;
        unordered_map<string, unordered_map<string, double>> edges;

        for (int i = 0; i < equations.size(); i++) {
            string a = equations[i][0], b = equations[i][1];
            double var = values[i];
            edges[a][b] = var, edges[b][a] = 1 / var;
            vertices.insert(a), vertices.insert(b);
        }

        for (const string& k : vertices) {
            for (const string& i : vertices) {
                for (const string& j : vertices) {
                    if (edges[i][k] && edges[j][k])
                        edges[i][j] = edges[i][k] * edges[k][j];
                }
            }
        }

        vector<double> res;
        for (vector<string>& q : queries) {
            string a = q[0], b = q[1];
            if (edges[a][b]) res.push_back(edges[a][b]);
            else res.push_back(-1);
        }

        return res;
    }
};