399. Evaluate Division

class Solution {
    public double[] calcEquation(String[][] equations, double[] values, String[][] queries) {
        Map<String, Map<String, Double>> map = new HashMap<>();
        for(int i = 0; i < equations.length; i++)
        {
            String[] eq = equations[i];
            double v = values[i];
            String from = eq[0], to = eq[1];
            if(!map.containsKey(from)) map.put(from, new HashMap<>());
            if(!map.containsKey(to)) map.put(to, new HashMap<>());
            map.get(from).put(to, v);
            map.get(from).put(from, 1.0);
            map.get(to).put(from, 1 / v);
            map.get(to).put(to, 1.0);
        }
        double[] re = new double[queries.length];
        for(int i = 0; i < queries.length; i++)
        {
            String[] q = queries[i];
            String from =  q[0], to = q[1];
            re[i] = calc(from, to, map);
        }
        return re;
    }

    double calc(String from, String to, Map<String, Map<String, Double>> map)
    {
        if(!map.containsKey(from)) return -1.0;
        if(map.get(from).containsKey(to)) return map.get(from).get(to);
        // if(map.containsKey(to) && map.get(to).containsKey(from)) return 1.0 / map.get(to).get(from);
        Queue<String> q = new LinkedList<>();
        Map<String, Double> fmap = map.get(from);
        q.offer(from);
        Set<String> visited = new HashSet<>();
        while(!q.isEmpty())
        {
            String poll = q.poll();
            System.out.println(poll);
            double val = fmap.get(poll);
            if(poll.equals(to)) return val;
            for(String next : map.get(poll).keySet())
            {
                // if(fmap.containsKey(next)) continue;
                double bridge = map.get(poll).get(next);
                fmap.put(next, val * bridge);
                if(visited.contains(next)) continue;
                visited.add(next);
                q.offer(next);
            }
       }
        return -1.0;
    }
}