結果

問題 No.1254 補強への架け橋
ユーザー tenten
提出日時 2022-08-16 11:25:15
言語 Java
(openjdk 23)
結果
AC  
実行時間 974 ms / 2,000 ms
コード長 3,581 bytes
コンパイル時間 2,396 ms
コンパイル使用メモリ 80,120 KB
実行使用メモリ 108,004 KB
最終ジャッジ日時 2024-10-03 03:29:30
合計ジャッジ時間 41,236 ms
ジャッジサーバーID
（参考情報） 		judge1 / judge2
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 123
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

import java.io.*;
import java.util.*;
public class Main {
    static ArrayList<HashMap<Integer, Integer>> graph = new ArrayList<>();
    static int[] depths;
    static int[] parents;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        ArrayList<Integer> ans = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            graph.add(new HashMap<>());
        }
        UnionFindTree uft = new UnionFindTree(n);
        int orgA = 0;
        int orgB = 0;
        for (int i = 1; i <= n; i++) {
            int left = sc.nextInt() - 1;
            int right = sc.nextInt() - 1;
            if (uft.same(left, right)) {
                ans.add(i);
                orgA = left;
                orgB = right;
            } else {
                uft.unite(left, right);
                graph.get(left).put(right, i);
                graph.get(right).put(left, i);
            }
        }
        depths = new int[n];
        parents = new int[n];
        setDepth(0, 0, 0);
        setAns(orgA, orgB, ans);
        StringBuilder sb = new StringBuilder();
        sb.append(ans.size()).append("\n");
        for (int i = 0; i < ans.size(); i++) {
            if (i > 0) {
                sb.append(" ");
            }
            sb.append(ans.get(i));
        }
        System.out.println(sb);
    }
    
    static void setAns(int left, int right, ArrayList<Integer> ans) {
        if (depths[left] < depths[right]) {
            setAns(right, left, ans);
            return;
        }
        while (depths[left] > depths[right]) {
            ans.add(graph.get(left).get(parents[left]));
            left = parents[left];
        }
        while (left != right) {
            ans.add(graph.get(left).get(parents[left]));
            left = parents[left];
            ans.add(graph.get(right).get(parents[right]));
            right = parents[right];
        }
    }
    
    static void setDepth(int idx, int p, int d) {
        depths[idx] = d;
        parents[idx] = p;
        for (int x : graph.get(idx).keySet()) {
            if (x == p) {
                continue;
            }
            setDepth(x, idx, d + 1);
        }
    }
    
    static class UnionFindTree {
        int[] parents;
        
        public UnionFindTree(int size) {
            parents = new int[size];
            for (int i = 0; i < size; i++) {
                parents[i] = i;
            }
        }
        
        public int find(int x) {
            if (x == parents[x]) {
                return x;
            } else {
                return parents[x] = find(parents[x]);
            }
        }
        
        public boolean same(int x, int y) {
            return find(x) == find(y);
        }
        
        public void unite(int x, int y) {
            parents[find(x)] = find(y);
        }
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}
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