graph_thread

package main.graph.command.impl;

import main.graph.Graph;
import main.graph.command.Executor;
import main.graph.vertex.unweight.Vertex;

import java.util.*;

public class FindMaxStreamByFordFulkersonAlgorithm implements Executor {

    @Override
    public Integer execute(Graph structure, Vertex... params) {

        Map<Integer, LinkedHashMap<Integer, Integer>> graph = structure.getGraph(); // FIXME:
        //

        Integer start = params[0].getVertexID();
        Integer finish = params[1].getVertexID();

        List<Integer> flows = new ArrayList<Integer>();

        int[] parent = new int[graph.size()];
        while (bfs(graph, parent, start, finish)) {
            int pathFlow = Integer.MAX_VALUE;

            for (int vertex = finish; vertex != start; vertex = parent[vertex]) {
                pathFlow = Math.min(pathFlow, graph.get(parent[vertex] + 1).get(vertex + 1));
            }

            for (int vertex = finish; vertex != start; vertex = parent[vertex]) {
                graph.get(parent[vertex] + 1).put(vertex + 1, graph.get(parent[vertex] + 1).get(vertex + 1) - pathFlow);
            }

            flows.add(pathFlow);
        }

        return sum(flows);
    }

    private boolean bfs(Map<Integer, LinkedHashMap<Integer, Integer>> graph, int parent[], Integer start, Integer finish) {

        boolean[] used = new boolean[graph.size()];

        Queue<Integer> queue = new ArrayDeque<>();
        queue.add(start + 1);
        used[start] = true;
        parent[start] = -1;

        while (!queue.isEmpty()) {
            int u = queue.poll() - 1;

            for (Integer vertex : graph.get(u + 1).keySet()) {
                if (!used[vertex - 1] && graph.get(u + 1).get(vertex) > 0) {
                    queue.add(vertex);
                    parent[vertex - 1] = u;
                    used[vertex - 1] = true;
                }
            }
        }

        return used[finish];
    }

    public int sum(List<Integer> ints) {
        return ints.isEmpty() ? 0 : ints.get(0) + sum(ints.subList(1, ints.size()));
    }
}

/*
5
1 2-2 3-3
2 3-3 4-4
3 5-2
4 5-1
5
*/