RUPC2016 Day2 A Gossip

問題

http://judge.u-aizu.ac.jp/onlinejudge/cdescription.jsp?cid=RitsCamp16Day2&pid=A

考察

が答え。
つまり最初に情報を持っているアイドルの間隔を2で割った値の最大値が解だが,アイドル1とアイドルNがそれぞれ情報持っているアイドルの中で一番間隔が近いアイドルとの間隔も先程の解の候補に含める。

ソースコード

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.NoSuchElementException;

public class Main{
	int N,M;
	int[] a;
	public void solve() {
		N = nextInt();
		M = nextInt();
		a = new int[M];
		for(int i = 0;i < M;i++)a[i] = nextInt();
		int ans = 0;
		for(int i = 0;i <= M;i++){
			if(i == 0)ans = Math.max(ans, a[i]-1);
			else if(i==M)ans = Math.max(ans,N-a[i-1]);
			else ans = Math.max(ans, (a[i]-a[i-1])/2);
		}
		out.println(ans);
	}

	public static void main(String[] args) {
		out.flush();
		new Main().solve();
		out.close();
	}

	/* Input */
	private static final InputStream in = System.in;
	private static final PrintWriter out = new PrintWriter(System.out);
	private final byte[] buffer = new byte[2048];
	private int p = 0;
	private int buflen = 0;

	private boolean hasNextByte() {
		if (p < buflen)
			return true;
		p = 0;
		try {
			buflen = in.read(buffer);
		} catch (IOException e) {
			e.printStackTrace();
		}
		if (buflen <= 0)
			return false;
		return true;
	}

	public boolean hasNext() {
		while (hasNextByte() && !isPrint(buffer[p])) {
			p++;
		}
		return hasNextByte();
	}

	private boolean isPrint(int ch) {
		if (ch >= '!' && ch <= '~')
			return true;
		return false;
	}

	private int nextByte() {
		if (!hasNextByte())
			return -1;
		return buffer[p++];
	}

	public String next() {
		if (!hasNext())
			throw new NoSuchElementException();
		StringBuilder sb = new StringBuilder();
		int b = -1;
		while (isPrint((b = nextByte()))) {
			sb.appendCodePoint(b);
		}
		return sb.toString();
	}

	public int nextInt() {
		return Integer.parseInt(next());
	}

	public long nextLong() {
		return Long.parseLong(next());
	}

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