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Copy pathdijkstra.java
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123 lines (104 loc) · 3.46 KB
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import java.util.Arrays;
public class DijkstraAlgorithm {
private static final int INFINITY = Integer.MAX_VALUE;
private static final int NO_PATH = -1;
public static void main(String[] args) {
testDijkstra();
}
private static void testDijkstra() {
int[][] graph1 = {
{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}
};
int startNode1 = 0;
runDijkstra(graph1, startNode1);
int[][] graph2 = {
{0, 3, 0, 0, 0, 0, 0, 4},
{3, 0, 1, 0, 0, 0, 0, 0},
{0, 1, 0, 8, 0, 0, 0, 0},
{0, 0, 8, 0, 2, 0, 0, 0},
{0, 0, 0, 2, 0, 6, 0, 0},
{0, 0, 0, 0, 6, 0, 7, 0},
{0, 0, 0, 0, 0, 7, 0, 9},
{4, 0, 0, 0, 0, 0, 9, 0}
};
int startNode2 = 2;
runDijkstra(graph2, startNode2);
int[][] graph3 = {
{0, 2, 4, 0, 0, 0},
{2, 0, 1, 7, 0, 0},
{4, 1, 0, 0, 3, 0},
{0, 7, 0, 0, 0, 1},
{0, 0, 3, 0, 0, 5},
{0, 0, 0, 1, 5, 0}
};
int startNode3 = 0;
runDijkstra(graph3, startNode3);
}
private static void runDijkstra(int[][] graph, int startNode) {
Graph g = new Graph(graph);
System.out.println("Graph:");
g.printGraph();
System.out.println("\nShortest distances from Node " + startNode + ":");
int[] shortestDistances = g.dijkstra(startNode);
printShortestDistances(shortestDistances);
System.out.println("-------------------------");
}
private static void printShortestDistances(int[] dist) {
System.out.println("Shortest distances:");
for (int i = 0; i < dist.length; i++) {
if (dist[i] == INFINITY) {
System.out.println("To " + i + ": No Path");
} else {
System.out.println("To " + i + ": " + dist[i]);
}
}
}
}
class Graph {
private final int[][] graph;
public Graph(int[][] graph) {
this.graph = graph;
}
public int[] dijkstra(int startNode) {
int vertices = graph.length;
int[] dist = new int[vertices];
boolean[] visited = new boolean[vertices];
Arrays.fill(dist, INFINITY);
dist[startNode] = 0;
for (int i = 0; i < vertices - 1; i++) {
int u = minDistance(dist, visited);
visited[u] = true;
for (int v = 0; v < vertices; v++) {
if (!visited[v] && graph[u][v] != 0 && dist[u] != INFINITY &&
dist[u] + graph[u][v] < dist[v]) {
dist[v] = dist[u] + graph[u][v];
}
}
}
return dist;
}
private int minDistance(int[] dist, boolean[] visited) {
int min = INFINITY;
int minIndex = -1;
for (int v = 0; v < dist.length; v++) {
if (!visited[v] && dist[v] < min) {
min = dist[v];
minIndex = v;
}
}
return minIndex;
}
public void printGraph() {
for (int[] row : graph) {
System.out.println(Arrays.toString(row));
}
}
}