結果

問題 No.806 木を道に
コンテスト
ユーザー holeguma
提出日時 2019-07-17 22:13:44
言語 Java
(openjdk 23)
結果
WA  
実行時間 -
コード長 4,327 bytes
コンパイル時間 2,731 ms
コンパイル使用メモリ 83,016 KB
実行使用メモリ 75,116 KB
最終ジャッジ日時 2024-12-23 11:37:18
合計ジャッジ時間 10,026 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 * 2
other AC * 9 WA * 18
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 # 

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Deque;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;

public class Main {

	static PrintWriter out;
	static InputReader ir;

	static void solve() {
		int n = ir.nextInt();
		Graph[] g = new Graph[n];
		for (int i = 0; i < n; i++) {
			g[i] = new Graph();
		}
		for (int i = 0; i < n - 1; i++) {
			int u = ir.nextInt() - 1;
			int v = ir.nextInt() - 1;
			g[u].add(new int[] { v, 1 });
			g[v].add(new int[] { u, 1 });
		}
		out.println(n - 1 - doubleSweep(g));
	}

	static class Graph extends ArrayList<int[]> {
	}

	static long doubleSweep(Graph[] g) {
		int s = 0;
		int n = g.length;
		while (s < n && g[s].size() == 0)
			s++;
		if (s == n)
			return 0;
		long[] dist = new long[n];
		int u = bfs(s, dist, g);
		int v = bfs(u, dist, g);
		return dist[v];
	}

	static int bfs(int s, long[] dist, Graph[] g) {
		Deque<Integer> que = new ArrayDeque<Integer>();
		Arrays.fill(dist, Long.MAX_VALUE / 2);
		que.offerLast(s);
		dist[s] = 0;
		int ret = -1;
		while (!que.isEmpty()) {
			int from = que.pollFirst();
			for (int i = 0; i < g[from].size(); i++) {
				int[] to = g[from].get(i);
				if (dist[to[0]] == Long.MAX_VALUE / 2) {
					dist[to[0]] = dist[from] + to[1];
					que.offerLast(to[0]);
				}
			}
		}
		for (int i = 0; i < g.length; i++)
			if (dist[i] != Long.MAX_VALUE / 2 && (ret == -1 || dist[ret] < dist[i]))
				ret = i;
		return ret;
	}

	public static void main(String[] args) {
		ir = new InputReader(System.in);
		out = new PrintWriter(System.out);
		solve();
		out.flush();
	}

	static class InputReader {

		private InputStream in;
		private byte[] buffer = new byte[1024];
		private int curbuf;
		private int lenbuf;

		public InputReader(InputStream in) {
			this.in = in;
			this.curbuf = this.lenbuf = 0;
		}

		public boolean hasNextByte() {
			if (curbuf >= lenbuf) {
				curbuf = 0;
				try {
					lenbuf = in.read(buffer);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (lenbuf <= 0)
					return false;
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[curbuf++];
			else
				return -1;
		}

		private boolean isSpaceChar(int c) {
			return !(c >= 33 && c <= 126);
		}

		private void skip() {
			while (hasNextByte() && isSpaceChar(buffer[curbuf]))
				curbuf++;
		}

		public boolean hasNext() {
			skip();
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (!isSpaceChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public int nextInt() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			long res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}

		public int[] nextIntArray(int n) {
			int[] a = new int[n];
			for (int i = 0; i < n; i++)
				a[i] = nextInt();
			return a;
		}

		public long[] nextLongArray(int n) {
			long[] a = new long[n];
			for (int i = 0; i < n; i++)
				a[i] = nextLong();
			return a;
		}

		public char[][] nextCharMap(int n, int m) {
			char[][] map = new char[n][m];
			for (int i = 0; i < n; i++)
				map[i] = next().toCharArray();
			return map;
		}
	}

	static void tr(Object... o) {
		out.println(Arrays.deepToString(o));
	}
}
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