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Added Dijkstra's Algorithm in JAVA #37

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83 changes: 83 additions & 0 deletions DijkstraAlgo.java
Original file line number Diff line number Diff line change
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// 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);
}
}