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class Solution {
    class Triple {
        String destination;
        double weight;

        public Triple(String d, double w) {
            this.destination = d;
            this.weight = w;
        }

    }

    public double[] calcEquation(List<List<String>> equations, double[] values, List<List<String>> queries) {
        HashMap<String, List<Triple>> adjList = new HashMap<>();
        
        for (int i = 0; i < equations.size(); i++) {
            String s1 = equations.get(i).get(0);
            String s2 = equations.get(i).get(1);

            double val = values[i];

            List<Triple> sourceNode = adjList.getOrDefault(s1, new ArrayList<Triple>());
            sourceNode.add(new Triple(s2, val));
            adjList.put(s1, sourceNode);

            double reverseVal = 1.0/val;
            List<Triple> destNode = adjList.getOrDefault(s2, new ArrayList<Triple>());
            destNode.add(new Triple(s1, reverseVal));
            adjList.put(s2, destNode);

        }

        double[] result = new double[queries.size()];
        int i = 0;

        for (List<String> list : queries) { 
            String s = list.get(0);
            String d = list.get(1);

            if (!adjList.containsKey(s) || !adjList.containsKey(d)) {
                result[i] = -1.00;
                i++;
                continue;
            }

            if (s.equals(d)) {
                result[i] = 1.00;
                i++;
                continue;
            }

            Set<String> visited = new HashSet<>();
            result[i] = dfs(s, d, adjList, visited);
            i++;
        }

        return result;

    }

    private double dfs(String source, String dest, HashMap<String, List<Triple>> adjList, Set<String> visited) {

        visited.add(source);
        double sum = -1;
        
        for (Triple t : adjList.get(source)) {
            if (visited.contains(t.destination)) {
                continue;
            }

            if (t.destination.equals(dest)) {
                return t.weight;
            }
            double val = dfs(t.destination, dest, adjList, visited);

            if (val >= 0) {
                sum = t.weight * val;
            }
        }

        return sum;
    }
}