桥和割点,以及图的遍历树

目录

什么是桥

寻找桥的算法

代码实现

什么是割点

​寻找割点的算法

代码实现


什么是桥

寻找桥的算法

代码实现

java 复制代码
import java.util.ArrayList;

public class FindBridges {

    private Graph G;
    private boolean[] visited;

    private int ord[];
    private int low[];
    private int cnt;

    private ArrayList<Edge> res;

    public FindBridges(Graph G){

        this.G = G;
        visited = new boolean[G.V()];

        res = new ArrayList<>();
        ord = new int[G.V()];
        low = new int[G.V()];
        cnt = 0;

        for(int v = 0; v < G.V(); v ++)
            if(!visited[v])
                dfs(v, v);
    }

    private void dfs(int v, int parent){

        visited[v] = true;
        ord[v] = cnt;
        low[v] = ord[v];
        cnt ++;

        for(int w: G.adj(v))
            if(!visited[w]){
                dfs(w, v);
                low[v] = Math.min(low[v], low[w]);
                if(low[w] > ord[v])
                    res.add(new Edge(v, w));
            }
            else if(w != parent)
                low[v] = Math.min(low[v], low[w]);
    }

    public ArrayList<Edge> result(){
        return res;
    }

    public static void main(String[] args){

        Graph g = new Graph("g.txt");
        FindBridges fb = new FindBridges(g);
        System.out.println("Bridges in g : " + fb.result());

        Graph g2 = new Graph("g2.txt");
        FindBridges fb2 = new FindBridges(g2);
        System.out.println("Bridges in g2 : " + fb2.result());

        Graph g3 = new Graph("g3.txt");
        FindBridges fb3 = new FindBridges(g3);
        System.out.println("Bridges in g3 : " + fb3.result());

        Graph tree = new Graph("tree.txt");
        FindBridges fb_tree = new FindBridges(tree);
        System.out.println("Bridges in tree : " + fb_tree.result());
    }
}

什么是割点

寻找割点的算法

孩子的数量是根据树来说的,而不是看根节点有多少个邻边,遍历树不同孩子数量也不同。

代码实现

java 复制代码
import java.util.HashSet;

public class FindCutPoints {

    private Graph G;
    private boolean[] visited;

    private int[] ord;
    private int[] low;
    private int cnt;

    private HashSet<Integer> res;

    public FindCutPoints(Graph G){

        this.G = G;
        visited = new boolean[G.V()];

        res = new HashSet<>();
        ord = new int[G.V()];
        low = new int[G.V()];
        cnt = 0;

        for(int v = 0; v < G.V(); v ++)
            if(!visited[v])
                dfs(v, v);
    }

    private void dfs(int v, int parent){

        visited[v] = true;
        ord[v] = cnt;
        low[v] = ord[v];
        cnt ++;

        int child = 0;

        for(int w: G.adj(v))
            if(!visited[w]){
                dfs(w, v);
                low[v] = Math.min(low[v], low[w]);

                if(v != parent && low[w] >= ord[v])
                    res.add(v);

                child ++;
                if(v == parent && child > 1)
                    res.add(v);
            }
            else if(w != parent)
                low[v] = Math.min(low[v], ord[w]);
    }

    public HashSet<Integer> result(){
        return res;
    }

    public static void main(String[] args){

        Graph g = new Graph("g.txt");
        FindCutPoints fc = new FindCutPoints(g);
        System.out.println("Cut Points in g : " + fc.result());

        Graph g2 = new Graph("g2.txt");
        FindCutPoints fc2 = new FindCutPoints(g2);
        System.out.println("Cut Points in g2 : " + fc2.result());

        Graph g3 = new Graph("g3.txt");
        FindCutPoints fc3 = new FindCutPoints(g3);
        System.out.println("Cut Points in g3 : " + fc3.result());

        Graph tree = new Graph("tree.txt");
        FindCutPoints fc4 = new FindCutPoints(tree);
        System.out.println("Cut Points in tree : " + fc4.result());

    }
}
相关推荐
Theodore_10222 小时前
4 设计模式原则之接口隔离原则
java·开发语言·设计模式·java-ee·接口隔离原则·javaee
网易独家音乐人Mike Zhou3 小时前
【卡尔曼滤波】数据预测Prediction观测器的理论推导及应用 C语言、Python实现(Kalman Filter)
c语言·python·单片机·物联网·算法·嵌入式·iot
冰帝海岸3 小时前
01-spring security认证笔记
java·笔记·spring
世间万物皆对象4 小时前
Spring Boot核心概念:日志管理
java·spring boot·单元测试
没书读了4 小时前
ssm框架-spring-spring声明式事务
java·数据库·spring
小二·4 小时前
java基础面试题笔记(基础篇)
java·笔记·python
开心工作室_kaic5 小时前
ssm161基于web的资源共享平台的共享与开发+jsp(论文+源码)_kaic
java·开发语言·前端
懒洋洋大魔王5 小时前
RocketMQ的使⽤
java·rocketmq·java-rocketmq
武子康5 小时前
Java-06 深入浅出 MyBatis - 一对一模型 SqlMapConfig 与 Mapper 详细讲解测试
java·开发语言·数据仓库·sql·mybatis·springboot·springcloud
转世成为计算机大神5 小时前
易考八股文之Java中的设计模式?
java·开发语言·设计模式