day 53 图论part5

文章目录

• [卡码网 107. 寻找存在的路线](#卡码网 107. 寻找存在的路线)

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卡码网 107. 寻找存在的路线

并查集基础题目，并查集的四种方法，初始化，每一个节点初始化指向自己，join方法，把两个节点加入到同一个集合中，isame方法，判断两个节点是否在同一个集合中，find方法，找到每一个节点的根节点，使用路径压缩。

import java.util.*;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int M = sc.nextInt();
        DisJoint disjoint = new DisJoint(N + 1);
        for (int i = 0; i < M;i++) {
            int s = sc.nextInt();
            int t = sc.nextInt();
            disjoint.join(s, t);
        }
        if (disjoint.isSame(sc.nextInt(), sc.nextInt())) {
            System.out.println("1");
        }
        else {
            System.out.println("0"); 
        }

    }
}

class DisJoint {
        private int[] father;
        public DisJoint(int N) {
            father = new int[N];
            for (int i = 0; i < N; i++) {
                father[i] = i;
            }
        }
        public int find (int n) {
            return n == father[n] ? n : (father[n] = find(father[n]));
        }
        public boolean isSame(int n, int m) {
            n = find(n);
            m = find(m);
            return n == m;
        }
        public void join(int n, int m) {
            n = find(n);
            m = find(m);
            if (n == m) {
                return;
            }
            father[n] = m;
        }
    }