Shortest Path Faster Algorithm

// C# implementation of SPFA
using System;
using System.Collections.Generic;

class GFG
{
    class pair
    { 
        public int first, second; 
        public pair(int first, int second) 
        { 
            this.first = first; 
            this.second = second; 
        } 
    }
     
// Graph is stored as vector of vector of pairs
// first element of pair store vertex
// second element of pair store weight
static List<pair> []graph = new List<pair>[100000];
 
// Function to add edges in the graph
// connecting a pair of vertex(frm) and weight
// to another vertex(to) in graph
static void addEdge(int frm, int to, int weight)
{
 
    graph[frm].Add(new pair( to, weight ));
}
 
// Function to print shortest distance from source
static void print_distance(int []d, int V)
{
    Console.Write("Vertex \t\t Distance"
        + " from source" +"\n");
 
    for (int i = 1; i <= V; i++) 
    {
        Console.Write("{0} \t\t {1}\n", i, d[i]);
    }
}
 
// Function to compute the SPF algorithm
static void shortestPathFaster(int S, int V)
{
    // Create array d to store shortest distance
    int []d = new int[V + 1];
 
    // Boolean array to check if vertex
    // is present in queue or not
    bool []inQueue = new bool[V + 1];
 
    // Initialize the distance from source to
    // other vertex as int.MaxValue(infinite)
    for (int i = 0; i <= V; i++) 
    {
        d[i] = int.MaxValue;
    }
    d[S] = 0;
 
    Queue<int> q = new Queue<int>();
    q.Enqueue(S);
    inQueue[S] = true;
 
    while (q.Count!=0)
    {
 
        // Take the front vertex from Queue
        int u = q.Peek();
        q.Dequeue();
        inQueue[u] = false;
 
        // Relaxing all the adjacent edges of
        // vertex taken from the Queue
        for (int i = 0; i < graph[u].Count; i++)
        {
 
            int v = graph[u][i].first;
            int weight = graph[u][i].second;
 
            if (d[v] > d[u] + weight) 
            {
                d[v] = d[u] + weight;
 
                // Check if vertex v is in Queue or not
                // if not then push it into the Queue
                if (!inQueue[v]) 
                {
                    q.Enqueue(v);
                    inQueue[v] = true;
                }
            }
        }
    }
 
    // Print the result
    print_distance(d, V);
}
 
// Driver code
public static void Main(String[] args)
{
    int V = 5;
    int S = 1;
    for (int i = 0; i < graph.Length; i++)
    {
        graph[i] = new List<pair>();
    }
     
    // Connect vertex a to b with weight w
    // addEdge(a, b, w)
    addEdge(1, 2, 1);
    addEdge(2, 3, 7);
    addEdge(2, 4, -2);
    addEdge(1, 3, 8);
    addEdge(1, 4, 9);
    addEdge(3, 4, 3);
    addEdge(2, 5, 3);
    addEdge(4, 5, -3);
 
    // Calling shortestPathFaster function
    shortestPathFaster(S, V);
}
}

// This code is contributed by PrinciRaj1992