Add adjacency matrix representation

Author: jcazevedo

src/main/java/com/packt/datastructuresandalg/lesson6/graph/AdjacencyMatrixGraph.java

@@ -0,0 +1,39 @@
+package com.packt.datastructuresandalg.lesson6.graph;
+
+public class AdjacencyMatrixGraph {
+    int[][] adj;
+
+    public AdjacencyMatrixGraph(int nodes) {
+        this.adj = new int[nodes][nodes];
+    }
+
+    public void addEdge(int u, int v) {
+        this.adj[u][v] = 1;
+    }
+
+    @Override
+    public String toString() {
+        String res = "";
+        for (int i = 0; i < this.adj.length; i++) {
+            res += (i + ":");
+            for (int j = 0; j < this.adj[i].length; j++)
+                res += (" " + adj[i][j]);
+            if (i + 1 < adj.length)
+                res += "\n";
+        }
+        return res;
+    }
+
+    public static void main(String [] args) {
+        AdjacencyMatrixGraph g = new AdjacencyMatrixGraph(6);
+        g.addEdge(0, 1);
+        g.addEdge(0, 3);
+        g.addEdge(1, 4);
+        g.addEdge(2, 4);
+        g.addEdge(2, 5);
+        g.addEdge(3, 1);
+        g.addEdge(4, 3);
+        g.addEdge(5, 5);
+        System.out.println(g);
+    }
+}