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1 | 1 | package me.premaseem.datastructure.graph; |
2 | 2 |
|
3 | | -import java.util.ArrayList; |
| 3 | + |
| 4 | +import java.util.LinkedList; |
4 | 5 |
|
5 | 6 | public class Graph { |
6 | 7 |
|
7 | | - ArrayList graphArray[]; |
| 8 | + int size; |
| 9 | + LinkedList<Integer> vertex[]; |
8 | 10 |
|
9 | | - public Graph(int numOfVertices) { |
10 | | - graphArray = new ArrayList[numOfVertices]; |
11 | | - for (int i = 0; i < graphArray.length; i++) { |
12 | | - graphArray[i] = new ArrayList<Integer>(); |
| 11 | + public Graph(int size){ |
| 12 | + this.size = size; |
| 13 | + vertex = new LinkedList[size]; |
| 14 | + for (int i = 0; i < size; i++) { |
| 15 | + vertex[i] = new LinkedList<>(); |
13 | 16 | } |
14 | | - |
15 | 17 | } |
16 | 18 |
|
17 | | - public void addEdge(int from, int to) { |
18 | | - graphArray[from].add(to); |
| 19 | + void addEdge(int p1, int p2 ){ |
| 20 | + if(p1 > vertex.length || p2 > vertex.length){ |
| 21 | + System.out.println("cannot add edge, vertex out of graph"); |
| 22 | + return; |
| 23 | + } |
| 24 | + vertex[p1].add(p2); |
19 | 25 | } |
20 | 26 |
|
21 | | - public void getAdjecents(int vertex) { |
22 | | - ArrayList edges = graphArray[vertex]; |
23 | | - for (Object i : edges) { |
24 | | - System.out.printf(" %s --> %s \n", vertex, i); |
25 | | - } |
| 27 | + public static void main(String[] args) { |
| 28 | + Graph g = new Graph(5); |
| 29 | + |
| 30 | + g.addEdge(0, 1); |
| 31 | + g.addEdge(0, 2); |
| 32 | + g.addEdge(1, 2); |
| 33 | + g.addEdge(2, 0); |
| 34 | + g.addEdge(2, 3); |
| 35 | + g.addEdge(3, 3); |
| 36 | + g.addEdge(0, 4); |
| 37 | + g.addEdge(4, 1); |
| 38 | + |
| 39 | + g.BFS(4); |
26 | 40 | } |
27 | 41 |
|
28 | | - public void printGraphEdges() { |
29 | | - for (int i = 0; i < graphArray.length; i++) { |
30 | | - for (Object obj : graphArray[i]) { |
31 | | - System.out.printf(" %s --> %s \n", i, obj); |
| 42 | + void BFS(int v){ |
| 43 | + |
| 44 | + // default marked as false for visited vertex |
| 45 | + boolean[] visited = new boolean[size]; |
| 46 | + |
| 47 | + // form a queue to ensure get first and then connected neighbours |
| 48 | + LinkedList<Integer> q = new LinkedList<>(); |
| 49 | + q.add(v); |
| 50 | + visited[v] = true; |
| 51 | + |
| 52 | + while(!q.isEmpty()){ |
| 53 | + Integer vert = q.poll(); |
| 54 | + System.out.println(" Visiting "+vert); |
| 55 | + |
| 56 | + // getting the adjacent and adding them to q if they not been visited before |
| 57 | + LinkedList<Integer> adj = this.vertex[vert]; |
| 58 | + |
| 59 | + for (Integer vo:adj) { |
| 60 | + if(!visited[vo]){ |
| 61 | + visited[vo] = true; |
| 62 | + q.add(vo); |
| 63 | + } |
32 | 64 | } |
33 | | - } |
34 | 65 |
|
| 66 | + } |
35 | 67 | } |
| 68 | + |
36 | 69 | } |
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