Merge pull request #1 from ArsiyaTasleem90250/ArsiyaTasleem90250-patch-1

Implement Dijkstra's algorithm for shortest paths

Author: ArsiyaTasleem90250

DijkstraShortestPath.java

@@ -0,0 +1,61 @@
+import java.util.*;
+
+public class DijkstraAlgorithm {
+    static class Edge {
+        int to;
+        int weight;
+        Edge(int t, int w) {
+            to = t;
+            weight = w;
+        }
+    }
+
+    public static int[] dijkstra(int n, List<List<Edge>> graph, int source) {
+        int[] dist = new int[n];
+        Arrays.fill(dist, Integer.MAX_VALUE);
+        dist[source] = 0;
+
+        PriorityQueue<int[]> pq = new PriorityQueue<>(Comparator.comparingInt(a -> a[1]));
+        pq.add(new int[]{source, 0});
+
+        boolean[] visited = new boolean[n];
+
+        while (!pq.isEmpty()) {
+            int[] node = pq.poll();
+            int u = node[0];
+
+            if (visited[u]) continue;
+            visited[u] = true;
+
+            for (Edge e : graph.get(u)) {
+                int v = e.to;
+                int w = e.weight;
+                if (dist[u] + w < dist[v]) {
+                    dist[v] = dist[u] + w;
+                    pq.add(new int[]{v, dist[v]});
+                }
+            }
+        }
+        return dist;
+    }
+
+    public static void main(String[] args) {
+        int n = 6;
+        List<List<Edge>> graph = new ArrayList<>();
+        for (int i = 0; i < n; i++) graph.add(new ArrayList<>());
+
+        graph.get(0).add(new Edge(1, 4));
+        graph.get(0).add(new Edge(2, 2));
+        graph.get(1).add(new Edge(3, 5));
+        graph.get(2).add(new Edge(1, 1));
+        graph.get(2).add(new Edge(3, 8));
+        graph.get(3).add(new Edge(4, 6));
+        graph.get(4).add(new Edge(5, 3));
+
+        int[] dist = dijkstra(n, graph, 0);
+
+        for (int i = 0; i < n; i++) {
+            System.out.println("Distance to " + i + " = " + dist[i]);
+        }
+    }
+}