【資料結構】Java實現圖的DFS和BFS
阿新 • • 發佈:2019-01-03
圖的深度優先遍歷(DFS)和廣度優先遍歷(BFS),DFS利用遞迴來實現比較易懂,DFS非遞迴就是將需要的遞迴的元素利用一個棧Stack來實現,以達到遞迴時候的順序,而BFS則是利用一個佇列Queue來實現。
package DataStructure;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;
public class Graph {
private int number = 9;
private boolean[] flag;
private String[] vertexs = { "A", "B", "C", "D", "E", "F", "G", "H", "I" };
private int[][] edges = {
{ 0, 1, 0, 0, 0, 1, 1, 0, 0 },
{ 1, 0, 1, 0, 0, 0, 1, 0, 1 },
{ 0, 1, 0, 1, 0, 0, 0, 0, 1 },
{ 0, 0, 1, 0, 1, 0, 1, 1, 1 },
{ 0, 0, 0, 1, 0, 1, 0, 1, 0 },
{ 1 , 0, 0, 0, 1, 0, 1, 0, 0 },
{ 0, 1, 0, 1, 0, 1, 0, 1, 0 },
{ 0, 0, 0, 1, 1, 0, 1, 0, 0 },
{ 0, 1, 1, 1, 0, 0, 0, 0, 0 }
};
void DFSTraverse() {
flag = new boolean[number];
for (int i = 0; i < number; i++) {
if (flag[i] == false ) {// 當前頂點沒有被訪問
DFS(i);
}
}
}
void DFS(int i) {
flag[i] = true;// 第i個頂點被訪問
System.out.print(vertexs[i] + " ");
for (int j = 0; j < number; j++) {
if (flag[j] == false && edges[i][j] == 1) {
DFS(j);
}
}
}
void DFS_Map(){
flag = new boolean[number];
Stack<Integer> stack =new Stack<Integer>();
for(int i=0;i<number;i++){
if(flag[i]==false){
flag[i]=true;
System.out.print(vertexs[i]+" ");
stack.push(i);
}
while(!stack.isEmpty()){
int k = stack.pop();
for(int j=0;j<number;j++){
if(edges[k][j]==1&&flag[j]==false){
flag[j]=true;
System.out.print(vertexs[j]+" ");
stack.push(j);
break;
}
}
}
}
}
void BFS_Map(){
flag = new boolean[number];
Queue<Integer> queue = new LinkedList<Integer>();
for(int i=0;i<number;i++){
if(flag[i]==false){
flag[i]=true;
System.out.print(vertexs[i]+" ");
queue.add(i);
while(!queue.isEmpty()){
int k=queue.poll();
for(int j=0;j<number;j++){
if(edges[k][j]==1&&flag[j]==false){
flag[j] = true;
System.out.print(vertexs[j]+" ");
queue.add(j);
}
}
}
}
}
}
public static void main(String[] args) {
Graph graph = new Graph();
System.out.println("DFS遞迴:");
graph.DFSTraverse();
System.out.println();
System.out.println("DFS非遞迴:");
graph.DFS_Map();
System.out.println();
System.out.println("BFS非遞迴:");
graph.BFS_Map();
}
}
程式執行結果: