Add Dijkstra algorithm implementation (Fixes #7112)

Author: prasanth-30011

graphs/Dijkstra.java

@@ -0,0 +1,41 @@
+package com.thealgorithms.graphs;
+
+import java.util.*;
+
+public class Dijkstra {
+
+    public static int[] dijkstra(List<List<int[]>> graph, int source) {
+        int n = graph.size();
+        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.offer(new int[]{source, 0});
+
+        while (!pq.isEmpty()) {
+            int[] curr = pq.poll();
+            int u = curr[0];
+            int d = curr[1];
+
+            if (d > dist[u]) continue;
+
+            for (int[] edge : graph.get(u)) {
+                int v = edge[0];
+                int w = edge[1];
+
+                if (w < 0) {
+                    throw new IllegalArgumentException("Negative weight detected");
+                }
+
+                if (dist[u] + w < dist[v]) {
+                    dist[v] = dist[u] + w;
+                    pq.offer(new int[]{v, dist[v]});
+                }
+            }
+        }
+        return dist;
+    }
+}