Dijkstras

src/main/java/com/thealgorithms/graph/Dijkstras.java

@@ -0,0 +1,62 @@
+package com.thealgorithms.graph;
+
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+import java.util.PriorityQueue;
+
+/**
+ * Implementation of Dijkstra's Algorithm.
+ * Finds the shortest path from a given source node to all other nodes in a weighted graph.
+ *
+ * @author: poorvikaa08
+ * @date: 19 October 2025 (Sunday)
+ * @wiki: https://en.wikipedia.org/wiki/Dijkstra%27s_algorithm
+ */
+public final class Dijkstras {
+
+    private Dijkstras() {
+        throw new AssertionError("Cannot instantiate utility class");
+    }
+
+    /**
+     * Computes the shortest distance from a source vertex to all other vertices.
+     *
+     * @param graph adjacency list representing the graph, where graph[u] contains pairs (v, weight)
+     * @param src   the source vertex
+     * @param v     total number of vertices
+     * @return an array of shortest distances from src to every vertex
+     */
+    public static int[] dijkstra(List<List<Node>> graph, int src, int v) {
+        int[] dist = new int[v];
+        Arrays.fill(dist, Integer.MAX_VALUE);
+        dist[src] = 0;
+
+        PriorityQueue<Node> pq = new PriorityQueue<>(Comparator.comparingInt(n -> n.weight));
+        pq.add(new Node(src, 0));
+
+        while (!pq.isEmpty()) {
+            Node curr = pq.poll();
+            for (Node neighbor : graph.get(curr.vertex)) {
+                int newDist = dist[curr.vertex] + neighbor.weight;
+                if (newDist < dist[neighbor.vertex]) {
+                    dist[neighbor.vertex] = newDist;
+                    pq.add(new Node(neighbor.vertex, newDist));
+                }
+            }
+        }
+
+        return dist;
+    }
+
+    /** Helper class representing an edge or connection to another vertex */
+    public static class Node {
+        int vertex;
+        int weight;
+
+        public Node(int vertex, int weight) {
+            this.vertex = vertex;
+            this.weight = weight;
+        }
+    }
+}