結果

問題 No.84 悪の算盤
ユーザー ziita
提出日時 2017-06-28 20:38:47
言語 Java
(openjdk 23)
結果
AC  
実行時間 52 ms / 5,000 ms
コード長 3,861 bytes
コンパイル時間 2,319 ms
コンパイル使用メモリ 79,656 KB
実行使用メモリ 37,464 KB
最終ジャッジ日時 2024-10-13 09:01:43
合計ジャッジ時間 3,550 ms
ジャッジサーバーID
（参考情報） 		judge4 / judge3
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 * 10
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.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.io.OutputStream;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.math.BigDecimal;
/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    }
    static class Task {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            long R = in.nextLong();
            long C = in.nextLong();
            if(R==C) out.println((R*C+3)/4-1);
            else out.println((R*C+1)/2-1);
        }
    }
    public static int[] sieveEratosthenes(int n) {
        if (n <= 32) {
            int[] primes = { 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31 };
            for (int i = 0; i < primes.length; i++) {
                if (n < primes[i]) {
                    return Arrays.copyOf(primes, i);
                }
            }
            return primes;
        }
        int u = n + 32;
        double lu = Math.log(u);
        int[] ret = new int[(int) (u / lu + u / lu / lu * 1.5)];
        ret[0] = 2;
        int pos = 1;
        int[] isnp = new int[(n + 1) / 32 / 2 + 1];
        int sup = (n + 1) / 32 / 2 + 1;
        int[] tprimes = { 3, 5, 7, 11, 13, 17, 19, 23, 29, 31 };
        for (int tp : tprimes) {
            ret[pos++] = tp;
            int[] ptn = new int[tp];
            for (int i = (tp - 3) / 2; i < tp << 5; i += tp)
                ptn[i >> 5] |= 1 << (i & 31);
            for (int j = 0; j < sup; j += tp) {
                for (int i = 0; i < tp && i + j < sup; i++) {
                    isnp[j + i] |= ptn[i];
                }
            }
        }
        // 3,5,7
        // 2x+3=n
        int[] magic = { 0, 1, 23, 2, 29, 24, 19, 3, 30, 27, 25, 11, 20, 8, 4, 13, 31, 22, 28, 18, 26, 10, 7, 12, 21, 17,
                9, 6, 16, 5, 15, 14 };
        int h = n / 2;
        for (int i = 0; i < sup; i++) {
            for (int j = ~isnp[i]; j != 0; j &= j - 1) {
                int pp = i << 5 | magic[(j & -j) * 0x076be629 >>> 27];
                int p = 2 * pp + 3;
                if (p > n)
                    break;
                ret[pos++] = p;
                if ((long) p * p > n)
                    continue;
                for (int q = (p * p - 3) / 2; q <= h; q += p)
                    isnp[q >> 5] |= 1 << q;
            }
        }
        return Arrays.copyOf(ret, pos);
    }
    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;
        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }
        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }
        public int nextInt() {
            return Integer.parseInt(next());
        }
        public long nextLong() {
            return Long.parseLong(next());
        }
    }
}
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