diff --git a/DijkstraAlgo.java b/DijkstraAlgo.java new file mode 100644 index 0000000..26f1a17 --- /dev/null +++ b/DijkstraAlgo.java @@ -0,0 +1,83 @@ +// This is one of the most important greedy algorithm for any Programming algorithm + + +import java.util.*; +import java.lang.*; +import java.io.*; + +class DijkstraAlgo { + // A utility function to find the vertex with minimum distance value + + static final int V = 9; + int minDistance(int dist[], Boolean sptSet[]) + { + // Initializing minimum value + int min = Integer.MAX_VALUE, min_index = -1; + + for (int v = 0; v < V; v++) + if (sptSet[v] == false && dist[v] <= min) { + min = dist[v]; + min_index = v; + } + + return min_index; + } + + // A method to print the prepared distance array + void printSolution(int dist[]) + { + System.out.println("Vertex \t\t Distance from Source"); + for (int i = 0; i < V; i++) + System.out.println(i + " \t\t " + dist[i]); + } + + // Method that implements Dijkstra's single source shortest path + // algorithm for a graph represented using adjacency matrix + // representation + void dijkstra(int graph[][], int src) + { + int dist[] = new int[V]; + + Boolean sptSet[] = new Boolean[V]; + + // Initialize all distances as INFINITE and stpSet[] as false + for (int i = 0; i < V; i++) { + dist[i] = Integer.MAX_VALUE; + sptSet[i] = false; + } + + // Distance of source vertex from itself is always 0 + dist[src] = 0; + + // Find shortest path for all vertices + for (int count = 0; count < V - 1; count++) { + int u = minDistance(dist, sptSet); + sptSet[u] = true; + + + for (int v = 0; v < V; v++) + if (!sptSet[v] && graph[u][v] != 0 && dist[u] != Integer.MAX_VALUE && dist[u] + graph[u][v] < dist[v]) + dist[v] = dist[u] + graph[u][v]; + } + + // print the constructed distance array + printSolution(dist); + } + + // Driver method + public static void main(String[] args) + { + /* Example Graph */ + int graph[][] = new int[][] { { 0, 4, 0, 0, 0, 0, 0, 8, 0 }, + { 4, 0, 8, 0, 0, 0, 0, 11, 0 }, + { 0, 8, 0, 7, 0, 4, 0, 0, 2 }, + { 0, 0, 7, 0, 9, 14, 0, 0, 0 }, + { 0, 0, 0, 9, 0, 10, 0, 0, 0 }, + { 0, 0, 4, 14, 10, 0, 2, 0, 0 }, + { 0, 0, 0, 0, 0, 2, 0, 1, 6 }, + { 8, 11, 0, 0, 0, 0, 1, 0, 7 }, + { 0, 0, 2, 0, 0, 0, 6, 7, 0 } }; + DijkstraAlgo d = new DijkstraAlgo(); + d.dijkstra(graph, 0); + } +} \ No newline at end of file