結果

問題 No.613 Solitude by the window
ユーザー zimpha
提出日時 2017-12-13 01:27:22
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 1,672 ms / 2,000 ms
コード長 2,329 bytes
コンパイル時間 619 ms
コンパイル使用メモリ 62,924 KB
最終ジャッジ日時 2025-01-05 05:11:36
ジャッジサーバーID
（参考情報） 		judge1 / judge4
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ファイルパターン 結果
sample AC * 3
other AC * 21
権限があれば一括ダウンロードができます
コンパイルメッセージ
main.cpp: In function ‘int main()’:
main.cpp:58:8: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   58 |   scanf("%lld%lld", &n, &m);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~
main.cpp:106:15: warning: ‘extra’ may be used uninitialized [-Wmaybe-uninitialized]
  106 |     n %= (end - extra);
      |          ~~~~~^~~~~~~~
main.cpp:67:22: note: ‘extra’ was declared here
   67 |     int64 x = 2 % m, extra, target = -1, end;
      |                      ^~~~~

ソースコード

diff #
プレゼンテーションモードにする

#include <cstdio>
#include <vector>
#include <bitset>
using int64 = long long;
int64 phi(int64 n) {
  int64 r = n;
  for (int64 i = 2; i * i <= n; ++i) {
    if (n % i == 0) {
      r = r / i * (i  -1);
      while (n % i == 0) n /= i;;
    }
  }
  if (n > 1) r = r / n * (n - 1);
  return r;
}
int64 pow_mod(int64 a, int64 n, int64 mod) {
  int64 r = 1;
  for (; n; n >>= 1) {
    if (n & 1) r = r * a % mod;
    a = a * a % mod;
  }
  return r;
}
int64 calc(int64 n, int64 mod) {
  // (2 + sqrt{3}) ^ (2^n) % mod
  n = pow_mod(2, n, mod - 1);
  int64 a = 1, b = 0;
  int64 c = 2, d = 1;
  for (; n; n >>= 1) {
    if (n & 1) {
      int64 u = (a * c + 3 * b * d) % mod;
      int64 v = (a * d + b * c) % mod;
      a = u, b = v;
    }
    int64 u = (c * c + d * d * 3) % mod;
    int64 v = 2 * c * d % mod;
    c = u, d = v;
  }
  return a;
}
int mark[34375000];
inline void set(int x) {
  mark[x >> 5] |= 1 << (x & 31);
}
inline int get(int x) {
  return mark[x >> 5] >> (x & 31) & 1;
}
int main() {
  int64 n, m;
  scanf("%lld%lld", &n, &m);
  if (m == 2) puts("0");
  else if (n <= 1000000) {
    int64 x = 2;
    for (int i = 1; i <= n; ++i) {
      x = (x * x + x * 4) % m;
    }
    printf("%lld\n", x);
  } else if (m == 3 || pow_mod(3, m / 2, m) == m - 1) {
    int64 x = 2 % m, extra, target = -1, end;
    if (m >= 100000000) {
      for (int i = 1; i <= n; ++i) {
        x = (x * x + 4 * x) % m;
        if ((x & 15) == 0) {
          if (get(x >> 4)) {
            target = x;
            end = i;
            break;
          }
          set(x >> 4);
        }
      }
    } else {
      set(2 % m);
      for (int i = 1; i <= n; ++i) {
        x = (x * x + 4 * x) % m;
        if (get(x)) {
          target = x;
          end = i;
          break;
        }
        set(x);
      }
    }
    if (target == -1) {
      printf("%lld\n", x);
      return 0;
    }
    x = 2 % m;
    for (int i = 0; i < n; ++i) {
      if (x == target) {
        extra = i;
        break;
      }
      x = (x * x + 4 * x) % m;
    }
    //printf("%lld %lld %lld\n", extra, end, target);
    n -= extra;
    n %= (end - extra);
    for (int i = 0; i < n; ++i) {
      x = (x * x + x * 4) % m;
    }
    printf("%lld\n", x);
  } else {
    int64 r = calc(n, m) * 2 % m + m - 2;
    printf("%lld\n", r % m);
  }
  return 0;
}
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