Submission #404215

#	Time	Username	Problem	Language	Result	Execution time	Memory
404215		rama_pang	Genetics (BOI18_genetics)	C++17	100 / 100	526 ms	25348 KiB

genetics

#include <bits/stdc++.h>
using namespace std;

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);

  int N, M, K;
  cin >> N >> M >> K;

  const int MAX = 16405;
  vector<bitset<MAX>> A(N, 0);

  for (int i = 0; i < N; i++) {
    string s;
    cin >> s;
    for (int j = 0; j < M; j++) {
      if (s[j] == 'A') A[i][j * 4 + 0] = 1;
      if (s[j] == 'C') A[i][j * 4 + 1] = 1;
      if (s[j] == 'T') A[i][j * 4 + 2] = 1;
      if (s[j] == 'G') A[i][j * 4 + 3] = 1;
    }
  }

  // Turn input into binary string
  M = 4 * M;
  K = 2 * K;

  // bit 0 = -1
  // bit 1 = +1
  // Take \sum A[x][i] * A[y][i]
  // (M - K) - K = differ
  // differ = M - 2K
  K = M - 2 * K;

  mt19937 rnd(123456789);
  vector<int> weight(N);
  for (int i = 0; i < N; i++) {
    weight[i] = (rnd()) % (1ll << 30);
  }

  long long sum_weight = 0;
  vector<long long> sum(M);
  for (int i = 0; i < N; i++) {
    sum_weight += weight[i];
    for (int j = 0; j < M; j++) {
      sum[j] += (A[i][j] == 0 ? -1 : 1) * weight[i];
    }
  }

  for (int i = 0; i < N; i++) {
    long long hashed = 0;
    for (int j = 0; j < M; j++) {
      int sgn = (A[i][j] == 0 ? -1 : 1);
      hashed += 1ll * sgn * (sum[j] - sgn * weight[i]);
    }
    long long should_be = 1ll * (sum_weight - weight[i]) * K;
    if (hashed == should_be) {
      cout << i + 1 << '\n';
      return 0;
    }
  }

  cout << -1 << '\n';
  return 0;
}

• Subtask 1: 27 / 27
• Subtask 2: 19 / 19
• Subtask 3: 28 / 28
• Subtask 4: 26 / 26