Merge pull request #226 from vinaytejab/master

Floyd_Warshall algo added

Author: abranhe

dynamic-programming/Floyd_Warshall.cpp

@@ -0,0 +1,112 @@
+#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;
+}