import java.util.*;

// shortest path
public class GraphAdjacentMatrix_BellmanFord {
    public static int empty = -1;

    private int adjMatrix[][];
    private int numVertices;
    private boolean visited[];
//    private int distance[];

    public GraphAdjacentMatrix_BellmanFord(int numVertices) {
        this.numVertices = numVertices;

        adjMatrix = new int[numVertices][numVertices];
        for (int i = 0; i < adjMatrix.length; i++) {
            for (int j = 0; j < adjMatrix[i].length; j++) {
                adjMatrix[i][j] = empty;
            }
        }

        visited = new boolean[numVertices];
    }


    public int getWeight(int i, int j){
        return adjMatrix[i][j];
    }

    public void setEdge(int i, int j, int weight) {
        adjMatrix[i][j] = weight;
    }

    public void delEdge(int i, int j) {
        adjMatrix[i][j] = empty;
    }

    public boolean isEdge(int i, int j) {
        return (adjMatrix[i][j] != -1);
    }

    public int first(int v1){
        int[] ary = this.adjMatrix[v1];
        int firstNeighborIndex = this.numVertices; // return n if none
        for (int i = 0; i < ary.length; i++) {
            if (ary[i] != empty){
                firstNeighborIndex = i;
                break;
            }
        }
        return firstNeighborIndex;
    }

    public int next(int v1, int v2){
        int[] ary = this.adjMatrix[v1];
        int nextNeighborIndex = this.numVertices; // return n if none
        for (int i = v2 + 1; i < ary.length; i++) {
            if (ary[i] != empty){
                nextNeighborIndex = i;
                break;
            }
        }
        return nextNeighborIndex; // return n if none
    }

    // calculate the shortest distances between the startingVertice to all other vertices
    public static int[] bellmanford(GraphAdjacentMatrix_BellmanFord gam, int startingVertice, Set<EdgeElemnt> edgeElemnts) {
        // initialize the final result array
        int[] distance = new int[gam.numVertices];
        for (int i = 0; i < distance.length; i++) {
            distance[i] = Integer.MAX_VALUE;
        }
        // the first vertex reached
        distance[startingVertice] = 0; // initialize first data - from startingVertice to each vertice (we will update this whenver we reach a vertex)

        // main work here
        for (int i = 1; i < gam.numVertices; i++) { // run |V| - 1 runs because the the final path can only have maximum |V| - 1 edges

            // process all edges each run (simply straightforward)
            for (EdgeElemnt ee : edgeElemnts) {
                // if the starting vertex in the directed graph is unreachable, skip it
                if (distance[ee.fromV] == Integer.MAX_VALUE) continue;

                if (distance[ee.toV] > (distance[ee.fromV] + ee.edgeWeight)) {
                    distance[ee.toV] = (distance[ee.fromV] + ee.edgeWeight);
                    System.out.print("");
                }
            }

        }

        // final round to check if there is a negative circle
        // if there is no negative circal, the distances of all should remain the same
        // however, if one of the distances is getting shorter and shorter each extra run, something is wrong.
        for (EdgeElemnt ee : edgeElemnts) {
            // if the starting vertex in the directed graph is unreachable, skip it
            if (distance[ee.fromV] == Integer.MAX_VALUE) continue;

            if (distance[ee.toV] > (distance[ee.fromV] + ee.edgeWeight)) {
                System.out.println("Graph contains negative weight cycle. Opration aborted");
                return distance;
            }
        }

        return distance;
    }


    public static class EdgeElemnt implements Comparable{
        public Integer fromV;
        public Integer toV;
        public Integer edgeWeight;

        public EdgeElemnt(Integer v1, Integer v2, Integer edgeWeight) {
            this.fromV = v1;
            this.toV = v2;
            this.edgeWeight = edgeWeight;
        }

        @Override
        public boolean equals(Object obj)
        {
            if(this == obj)
                return true;
            if(obj == null || obj.getClass()!= this.getClass())
                return false;

            // type casting of the argument.
            EdgeElemnt geek = (EdgeElemnt) obj;
            return  (geek.fromV == this.fromV && geek.toV == this.toV) || (geek.fromV == this.toV && geek.toV == this.fromV);
        }

        @Override
        public int hashCode() {
            return Objects.hash(fromV + toV);
        }

        @Override
        public int compareTo(Object o) {
            EdgeElemnt o1 = (EdgeElemnt) o;
            return this.edgeWeight.compareTo(o1.edgeWeight);
        }

        @Override
        public String toString() {
            return " " + edgeWeight;
//            return "EdgeElemnt{" +
//                    "fromV=" + fromV +
//                    ", toV='" + toV +
//                    ", edgeWeight=" + edgeWeight +
//                    '}';
        }
    }



    // Imagine we convert the length n into n vertices and use BFS;
    // we will be making many redundant waves until we reach a vertex
    // Therefore, this method here is to help us save those steps and find the next vertex right away
    // (we could use minHeap to replace this method)
    //
    // find the shorted distance from startingVertice to D so far; this will be our next starting point
    private int minVertex(int[] distance) {
        int nextVWithShortestDistance = empty; // if all vertices are visited
        // initialize v to some unvisited vertex
        int i;
        for (i = 0; i < this.numVertices; i++) {
            if (!visited[i]) {
                nextVWithShortestDistance = i;
                break;
            }
        }
        // find the smallest D value
        for (i++; i < this.numVertices; i++) {
            if (!visited[i] && distance[i] < distance[nextVWithShortestDistance]) {
                nextVWithShortestDistance = i;
            }
        }

        return nextVWithShortestDistance;
    }

    private void Previsit(boolean[][] graph, int v) {
        System.out.println("Previsit: " + v);
    }

    private void Postvisit(boolean[][] graph, int v) {
        System.out.println("Postvisit: " + v);
    }

    public String toString() {
        StringBuilder s = new StringBuilder();
        for (int i = 0; i < numVertices; i++) {
            s.append(i + ": ");
            for (int j : adjMatrix[i]) {
                s.append((i != empty?1:0) + " ");
            }
            s.append("\n");
        }
        return s.toString();
    }

    public static void main(String[] args) {
        GraphAdjacentMatrix_BellmanFord gam = new GraphAdjacentMatrix_BellmanFord(8);

        // directed graph
        Set<EdgeElemnt> edgeElemnts = new HashSet<>();
        edgeElemnts.add(new EdgeElemnt(1, 2, -1));
        edgeElemnts.add(new EdgeElemnt(1, 3, 4));
        edgeElemnts.add(new EdgeElemnt(2, 3, 3));
        edgeElemnts.add(new EdgeElemnt(2, 4, 2));
        edgeElemnts.add(new EdgeElemnt(2, 5, 2));
        edgeElemnts.add(new EdgeElemnt(4, 3, 5));
        edgeElemnts.add(new EdgeElemnt(4, 2, 1));
        edgeElemnts.add(new EdgeElemnt(5, 4, -3));

        int[] distances = bellmanford(gam, 1, edgeElemnts);
        printArray(distances);

        System.out.printf("the shortest distance between %d and %d = %d %n", 1, 1, distances[1]);
        System.out.printf("the shortest distance between %d and %d = %d %n", 1, 2, distances[2]);
        System.out.printf("the shortest distance between %d and %d = %d %n", 1, 3, distances[3]);
        System.out.printf("the shortest distance between %d and %d = %d %n", 1, 4, distances[4]);
        System.out.printf("the shortest distance between %d and %d = %d %n", 1, 5, distances[5]);

        System.out.println();
    }


    ////////// UTIL ///////////

    private static void printArray(int[] ary){
        for (int i = 0; i < ary.length; i++) {
            System.out.printf("%4d" , ary[i]);
        }
        System.out.println();
    }

}