TheAlgorithms-C-Plus-Plus/dynamic_programming/Floyd-Warshall.cpp

#include <iostream>
#include <limits.h>
#include <string.h>

using namespace std;

//Wrapper class for storing a graph
class Graph
{
public:
	int vertexNum;
	int **edges;

	//Constructs a graph with V vertices and E edges
	Graph(int V)
	{
		this->vertexNum = V;
		this->edges = (int **)malloc(V * sizeof(int *));
		for (int i = 0; i < V; i++)
		{
			this->edges[i] = (int *)malloc(V * sizeof(int));
			for (int j = 0; j < V; j++)
				this->edges[i][j] = INT_MAX;
			this->edges[i][i] = 0;
		}
	}

	//Adds the given edge to the graph
	void addEdge(int src, int dst, int weight)
	{
		this->edges[src][dst] = weight;
	}
};

//Utility function to print distances
void print(int dist[], int V)
{
	cout << "\nThe Distance matrix for Floyd - Warshall" << endl;
	for (int i = 0; i < V; i++)
	{
		for (int j = 0; j < V; j++)
		{

			if (dist[i * V + j] != INT_MAX)
				cout << dist[i * V + j] << "\t";
			else
				cout << "INF"
					 << "\t";
		}
		cout << endl;
	}
}

//The main function that finds the shortest path from a vertex
//to all other vertices using Floyd-Warshall Algorithm.
void FloydWarshall(Graph graph)
{
	int V = graph.vertexNum;
	int dist[V][V];

	//Initialise distance array
	for (int i = 0; i < V; i++)
		for (int j = 0; j < V; j++)
			dist[i][j] = graph.edges[i][j];

	//Calculate distances
	for (int k = 0; k < V; k++)
		//Choose an intermediate vertex

		for (int i = 0; i < V; i++)
			//Choose a source vertex for given intermediate

			for (int j = 0; j < V; j++)
				//Choose a destination vertex for above source vertex

				if (dist[i][k] != INT_MAX && dist[k][j] != INT_MAX && dist[i][k] + dist[k][j] < dist[i][j])
					//If the distance through intermediate vertex is less than direct edge then update value in distance array
					dist[i][j] = dist[i][k] + dist[k][j];

	//Convert 2d array to 1d array for print
	int dist1d[V * V];
	for (int i = 0; i < V; i++)
		for (int j = 0; j < V; j++)
			dist1d[i * V + j] = dist[i][j];

	print(dist1d, V);
}

//Driver Function
int main()
{
	int V, E;
	int src, dst, weight;
	cout << "Enter number of vertices: ";
	cin >> V;
	cout << "Enter number of edges: ";
	cin >> E;
	Graph G(V);
	for (int i = 0; i < E; i++)
	{
		cout << "\nEdge " << i + 1 << "\nEnter source: ";
		cin >> src;
		cout << "Enter destination: ";
		cin >> dst;
		cout << "Enter weight: ";
		cin >> weight;
		G.addEdge(src, dst, weight);
	}
	FloydWarshall(G);

	return 0;
}