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
dying_man18 分钟前
LeetCode--42.接雨水
算法·leetcode
留不住丨晚霞27 分钟前
说说SpringBoot常用的注解?
java·开发语言
华科云商xiao徐33 分钟前
Java多线程爬虫动态线程管理实现
java·爬虫·数据挖掘
柒七爱吃麻辣烫42 分钟前
八股文系列-----SpringBoot自动配置的流程
java·spring boot·rpc
M1A11 小时前
Java 面试系列第一弹:基础问题大盘点
java·后端·mysql
发仔1231 小时前
Dubbo介绍及示例用法
java·dubbo
vortex51 小时前
算法设计与分析 知识总结
算法
goxingman1 小时前
关于使用idea打包的时候报错,Maven提示乱码java: �Ҳ�������
java·maven·intellij-idea
艾莉丝努力练剑1 小时前
【C语言】学习过程教训与经验杂谈:思想准备、知识回顾(三)
c语言·开发语言·数据结构·学习·算法
ZZZS05161 小时前
stack栈练习
c++·笔记·学习·算法·动态规划