[백준] 1717번 - 집합의 표현 [Java]

https://www.acmicpc.net/problem/1717

 

[백준] 1717번 - 집합의 표현 [Java]

[백준] 1717번 - 집합의 표현 [Java]

---

1.  아이디어

 

유니온 파인드 알고리즘으로 해결할 수 있다.

---

2. 문제풀이

 

각 집합의 합집합 연산은 union, 같은 집합에 있는 지 확인하는 연산은 find로 구할 수 있다.

---

3. 코드

 

import java.io.*;
import java.util.*;

public class Main {

    private static int[] p;

    private static int[] make(int N) {
        int[] arr = new int[1 + N];
        for (int i = 1; i <= N; i++) {
            arr[i] = i;
        }
        return arr;
    }

    private static int find(int x) {
        if (x == p[x]) return x;
        return p[x] = find(p[x]);
    }

    private static void union(int x, int y) {
        p[find(y)] = find(x);
    }

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st = new StringTokenizer(br.readLine());

        int N = Integer.parseInt(st.nextToken());
        int M = Integer.parseInt(st.nextToken());

        p = make(N);

        for (int i = 0; i < M; i++) {
            st = new StringTokenizer(br.readLine());
            int bit = Integer.parseInt(st.nextToken());
            int A = Integer.parseInt(st.nextToken());
            int B = Integer.parseInt(st.nextToken());

            if (bit == 0) {
                union(A, B);
            } else {
                if (find(A) == find(B)) {
                    bw.write("YES\n");
                } else {
                    bw.write("NO\n");
                }
            }
        }

        bw.flush();
    }
}

---

4. 후기