Problem:
Single Source Shortest Path (Negative Edges)

Input

An edge-weighted graph G (V, E) and the source r.

|V| |E| r
s0 t0 d0
s1 t1 d1
:
s|E|-1 t|E|-1 d|E|-1

|V| is the number of vertices and |E| is the number of edges in G. The graph vertices are named with the numbers 0, 1,..., |V|-1 respectively. r is the source of the graph.

si and ti represent source and target vertices of i-th edge (directed) and di represents the cost of the i-th edge.

Output

If the graph contains a negative cycle (a cycle whose sum of edge costs is a negative value) which is reachable from the source r, print

NEGATIVE CYCLE

in a line.

Otherwise, print

c0
c1
:
c|V|-1

The output consists of |V| lines. Print the cost of the shortest path from the source r to each vertex 0, 1, ... |V|-1 in order. If there is no path from the source to a vertex, print "INF".

Constraints

1 ≤ |V| ≤ 1000

0 ≤ |E| ≤ 2000

-10000 ≤ di ≤ 10000

There are no parallel edges

There are no self-loops

Sample Input 1

4 5 0
0 1 2
0 2 3
1 2 -5
1 3 1
2 3 2

Sample Output 1

0
2
-3
-1

Sample Input 2

4 6 0
0 1 2
0 2 3
1 2 -5
1 3 1
2 3 2
3 1 0

Sample Output 2

NEGATIVE CYCLE

Sample Input 3

4 5 1
0 1 2
0 2 3
1 2 -5
1 3 1
2 3 2

Sample Output 3

INF
0
-5
-3

Solution in C# (judge verdict: Accepted)

using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Collections.Generic;
using System.Diagnostics;
//using System.Numerics;
using Enu = System.Linq.Enumerable;

public class Program
{
    public void Solve()
    {
        int V = Reader.Int(), E = Reader.Int(), S = Reader.Int();
        var G = Enu.Range(0, V).Select(i => new List<Edge>()).ToArray();

        for (int i = 0; i < E; i++)
            G[Reader.Int()].Add(new Edge(Reader.Int(), Reader.Int()));
        var dist = ShortestPath(S, G);
        if (dist == null)
            Console.WriteLine("NEGATIVE CYCLE");
        else
            for (int a = 0; a < V; a++)
                if (dist[a] == INF) Console.WriteLine("INF");
                else Console.WriteLine(dist[a]);

        Console.ReadLine();
    }

    static readonly int INF = (int)1e9;
    static int[] ShortestPath(int start, List<Edge>[] G)
    {
        int N = G.Length;
        bool[] inQue = new bool[N];
        int[] count = new int[N];
        var que = new Queue<int>();
        que.Enqueue(start);
        var minCost = new int[N];
        for (int i = 0; i < N; i++) minCost[i] = INF;
        minCost[start] = 0;

        while (que.Count > 0)
        {
            int v = que.Dequeue();
            inQue[v] = false;
            foreach (var e in G[v])
                if (minCost[v] + e.cost < minCost[e.to])
                {
                    if (++count[e.to] == N) return null;
                    minCost[e.to] = minCost[v] + e.cost;
                    if (!inQue[e.to])
                    {
                        inQue[e.to] = true;
                        que.Enqueue(e.to);
                    }
                }
        }
        return minCost;
    }

    struct Edge
    {
        public int to;
        public int cost;
        public Edge(int to, int cost) { this.to = to; this.cost = cost; }
    }

}


class Entry { static void Main() { new Program().Solve(); } }
class Reader
{
    static TextReader reader = Console.In;
    static readonly char[] separator = { ' ' };
    static readonly StringSplitOptions op = StringSplitOptions.RemoveEmptyEntries;
    static string[] A = new string[0];
    static int i;
    static void Init() { A = new string[0]; }
    public static void Set(TextReader r) { reader = r; Init(); }
    public static void Set(string file) { reader = new StreamReader(file); Init(); }
    public static bool HasNext() { return CheckNext(); }
    public static string String() { return Next(); }
    public static int Int() { return int.Parse(Next()); }
    public static long Long() { return long.Parse(Next()); }
    public static double Double() { return double.Parse(Next()); }
    public static int[] IntLine() { return Array.ConvertAll(Split(Line()), int.Parse); }
    public static int[] IntArray(int N) { return Range(N, Int); }
    public static int[][] IntTable(int H) { return Range(H, IntLine); }
    public static string[] StringArray(int N) { return Range(N, Next); }
    public static string[][] StringTable(int N) { return Range(N, () => Split(Line())); }
    public static string Line() { return reader.ReadLine().Trim(); }
    static T[] Range<T>(int N, Func<T> f) { return Enu.Range(0, N).Select(i => f()).ToArray(); }
    static string[] Split(string s) { return s.Split(separator, op); }
    static string Next() { CheckNext(); return A[i++]; }
    static bool CheckNext()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return CheckNext();
        A = Split(line);
        i = 0;
        return true;
    }
}