120 lines
3.0 KiB
Java
120 lines
3.0 KiB
Java
package com.study.graph;
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import java.util.LinkedList;
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import java.util.Queue;
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/**
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* @author ldb
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* @date 2019-10-23 15:10
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*/
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public class Graph {
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private int v;
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private LinkedList<Integer> adj[]; // 邻接表
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public Graph(int v) {
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this.v = v;
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adj = new LinkedList[v];
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for (int i = 0; i < v; ++i) {
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adj[i] = new LinkedList<>();
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}
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}
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/**
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* 添加边
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*
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* @param s 顶点
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* @param t 顶点
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*/
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public void addEdge(int s, int t) { // 无向图一条边存两次
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adj[s].add(t);
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adj[t].add(s);
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}
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public void bfs(int s, int t) {
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if (s == t) return;
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// visited是用来记录已经被访问的顶点，用来避免顶点被重复访问。
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boolean[] visited = new boolean[v];
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visited[s] = true;
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// queue是一个队列，用来存储已经被访问、但相连的顶点还没有被访问的顶点。
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Queue<Integer> queue = new LinkedList<>();
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queue.add(s);
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// prev用来记录搜索路径。
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int[] prev = new int[v];
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for (int i = 0; i < v; ++i) {
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prev[i] = -1;
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}
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while (queue.size() != 0) {
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int w = queue.poll();
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for (int i = 0; i < adj[w].size(); ++i) {
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int q = adj[w].get(i);
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if (!visited[q]) {
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prev[q] = w;
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if (q == t) {
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print(prev, s, t);
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return;
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}
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visited[q] = true;
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queue.add(q);
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}
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}
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}
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}
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private void print(int[] prev, int s, int t) { // 递归打印 s->t 的路径
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if (prev[t] != -1 && t != s) {
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print(prev, s, prev[t]);
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}
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System.out.print(t + " ");
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}
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public static void main(String[] args) {
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Graph graph = new Graph(8);
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graph.addEdge(0,1);
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graph.addEdge(0,3);
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graph.addEdge(1,2);
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graph.addEdge(1,4);
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graph.addEdge(2,5);
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graph.addEdge(4,5);
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graph.addEdge(4,6);
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graph.addEdge(5,7);
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graph.addEdge(6,7);
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// graph.bfs(0,6);
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// 深度优先
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graph.dfs(0, 6);
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}
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boolean found = false; // 全局变量或者类成员变量
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public void dfs(int s, int t) {
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found = false;
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boolean[] visited = new boolean[v];
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int[] prev = new int[v];
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for (int i = 0; i < v; ++i) {
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prev[i] = -1;
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}
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recurDfs(s, t, visited, prev);
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print(prev, s, t);
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}
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private void recurDfs(int w, int t, boolean[] visited, int[] prev) {
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if (found == true) return;
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visited[w] = true;
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if (w == t) {
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found = true;
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return;
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}
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for (int i = 0; i < adj[w].size(); ++i) {
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int q = adj[w].get(i);
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if (!visited[q]) {
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prev[q] = w;
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recurDfs(q, t, visited, prev);
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}
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}
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}
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}
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