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
异常君几秒前
线程池隐患解析:为何阿里巴巴拒绝 Executors
java·后端·代码规范
Java技术小馆6 分钟前
SpringBoot中暗藏的设计模式
java·面试·架构
xiguolangzi7 分钟前
《springBoot3 中使用redis》
java
李菠菜14 分钟前
非SpringBoot环境下Jedis集群操作Redis实战指南
java·redis
丶Darling.22 分钟前
26考研 | 王道 | 数据结构 | 第八章 排序
数据结构·考研·排序算法
不当菜虚困26 分钟前
JAVA设计模式——(四)门面模式
java·开发语言·设计模式
BB_CC_DD30 分钟前
四. 以Annoy算法建树的方式聚类清洗图像数据集,一次建树,无限次聚类搜索,提升聚类搜索效率。(附完整代码)
深度学习·算法·聚类
m0Java门徒34 分钟前
面向对象编程核心:封装、继承、多态与 static 关键字深度解析
java·运维·开发语言·intellij-idea·idea
无心水1 小时前
【Java面试笔记:基础】8.对比Vector、ArrayList、LinkedList有何区别?
java·笔记·面试·vector·arraylist·linkedlist
我也不曾来过11 小时前
list底层原理
数据结构·c++·list