結果

問題 No.732 3PrimeCounting
ユーザー hiromi_ayase
提出日時 2018-09-08 15:22:52
言語 Java
(openjdk 23)
結果
AC  
実行時間 2,640 ms / 3,000 ms
コード長 4,388 bytes
コンパイル時間 2,479 ms
コンパイル使用メモリ 82,908 KB
実行使用メモリ 42,284 KB
最終ジャッジ日時 2024-12-16 06:42:09
合計ジャッジ時間 37,721 ms
ジャッジサーバーID
（参考情報） 		judge3 / judge2
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ファイルパターン 結果
other AC * 89
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ソースコード

diff # 

import java.util.Arrays;

public class Main {
 
  private static void solve() {
    int n = ni();
    int[] primes = sieveEratosthenes(3 * n);
    boolean[] isPrime = new boolean[3 * n + 1];
    for (int p : primes) {
      isPrime[p] = true;
    }

    long[] cnt = new long[3 * n];

    long ret = 0;
    for (int i = 2; primes[i] <= n; i ++) {
      int c = primes[i];
      int b = primes[i - 1];
      for (int j = 0; primes[j] < primes[i - 1]; j ++) {
        int a = primes[j];
        cnt[b + a] ++;
      }

      for (int j = 0; j <= 2*c ; j++) {
        if (isPrime[c + j] && cnt[j] > 0) {
          ret += cnt[j];
        }
      }
    }
    System.out.println(ret);
  }
  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;
      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);
  }

  public static void main(String[] args) {
    new Thread(null, new Runnable() {
      @Override
      public void run() {
        long start = System.currentTimeMillis();
        String debug = args.length > 0 ? args[0] : null;
        if (debug != null) {
          try {
            is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
          } catch (Exception e) {
            throw new RuntimeException(e);
          }
        }
        reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
        solve();
        out.flush();
        tr((System.currentTimeMillis() - start) + "ms");
      }
    }, "", 64000000).start();
  }
 
  private static java.io.InputStream is = System.in;
  private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
  private static java.util.StringTokenizer tokenizer = null;
  private static java.io.BufferedReader reader;
 
  public static String next() {
    while (tokenizer == null || !tokenizer.hasMoreTokens()) {
      try {
        tokenizer = new java.util.StringTokenizer(reader.readLine());
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
    return tokenizer.nextToken();
  }
 
  private static double nd() {
    return Double.parseDouble(next());
  }
 
  private static long nl() {
    return Long.parseLong(next());
  }
 
  private static int[] na(int n) {
    int[] a = new int[n];
    for (int i = 0; i < n; i++)
      a[i] = ni();
    return a;
  }
 
  private static char[] ns() {
    return next().toCharArray();
  }
 
  private static long[] nal(int n) {
    long[] a = new long[n];
    for (int i = 0; i < n; i++)
      a[i] = nl();
    return a;
  }
 
  private static int[][] ntable(int n, int m) {
    int[][] table = new int[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[i][j] = ni();
      }
    }
    return table;
  }
 
  private static int[][] nlist(int n, int m) {
    int[][] table = new int[m][n];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[j][i] = ni();
      }
    }
    return table;
  }
 
  private static int ni() {
    return Integer.parseInt(next());
  }
 
  private static void tr(Object... o) {
    if (is != System.in)
      System.out.println(java.util.Arrays.deepToString(o));
  }
 }
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