9.1. Flow Network

public class MaxFlow {
    private Map<Edge, Double> flow_map;
    private double maxflow;

    public MaxFlow(Graph graph) {
        init(graph);
    }

    public void init(Graph graph) {
        flow_map = new HashMap<>();
        maxflow = 0;

        for (Edge edge : graph.getAllEdges())
            flow_map.put(edge, 0d);
    }
}

public double getMaxFlow() {
    return maxflow;
}

public double getResidual(Edge edge) {
    return edge.getWeight() - flow_map.get(edge);
}

public void updateFlow(List<Edge> path, double flow) {
    path.forEach(e -> updateFlow(e, flow));
    maxflow += flow;
}

public void updateFlow(Edge edge, double flow) {
    Double prev = flow_map.getOrDefault(edge, 0d);
    flow_map.put(edge, prev + flow);
}