Problem p02618 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;

mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());

int N, D;
vector<int> C;
vector<vector<int>> S;

vector<int> ans;

void Read(bool local = false) {
  N = 26;
  if (local) {
    D = 365;
  } else {
    cin >> D;
  }
  C.resize(N);
  for (int i = 0; i < N; i++) {
    if (local) {
      C[i] = rnd() % 100;
    } else {
      cin >> C[i];
    }
  }
  S.resize(D);
  for (int i = 0; i < D; i++) {
    S[i].resize(N);
    for (int j = 0; j < N; j++) {
      if (local) {
        S[i][j] = rnd() % 20000;
      } else {
        cin >> S[i][j];
      }
    }
  }
  ans.assign(D, 0);
}

void Write() {
  for (auto i : ans) {
    cout << i + 1 << "\n";
  }
}

int Arithmetic(int n) { return n * (n - 1) / 2; }

vector<set<int>> Build(vector<int> a) {
  vector<set<int>> occ(N);
  for (int i = 0; i < D; i++) {
    occ[a[i]].insert(i);
  }
  for (int i = 0; i < N; i++) {
    occ[i].insert(-1);
    occ[i].insert(D);
  }
  return occ;
}

int Evaluate(vector<int> a) {
  vector<int> last(N, -1);
  int score = 0;
  for (int i = 0; i < D; i++) {
    score += S[i][a[i]];
    last[a[i]] = i;
    for (int j = 0; j < 26; j++) {
      score -= C[j] * (i - last[j]);
    }
  }
  return score;
}

int Evaluate(int init_score, const vector<int> &a, const vector<set<int>> &occ,
             int d, int q) {
  if (a[d] == q)
    return init_score;
  const set<int> &cur = occ[a[d]];
  auto pos = cur.lower_bound(d);
  int lst = *prev(pos);
  int nxt = *next(pos);

  int score = init_score;
  score += C[a[d]] *
           (Arithmetic(nxt - d) + Arithmetic(d - lst) - Arithmetic(nxt - lst));

  pos = occ[q].upper_bound(d);
  lst = *prev(pos);
  nxt = *pos;
  score -= C[q] *
           (Arithmetic(nxt - d) + Arithmetic(d - lst) - Arithmetic(nxt - lst));

  score -= S[d][a[d]];
  score += S[d][q];

  return score;
}

void Change(int &init_score, vector<int> &a, vector<set<int>> &occ, int d,
            int q) {
  int new_score = Evaluate(init_score, a, occ, d, q);
  init_score = new_score;
  occ[a[d]].erase(d);
  a[d] = q;
  occ[a[d]].insert(d);
}

void Solve() {
  vector<int> a(D);
  for (int i = 0; i < D; i++) {
    a[i] = rnd() % N;
  }
  int score = Evaluate(a);
  vector<set<int>> occ = Build(a);

  double temp = 10000;
  double cooling_rate = 0.999999;
  double absolute_zero = 0.00000001;
  int rep = 3e6;
  while (rep--) {
    int d = rnd() % D;
    int q = rnd() % N;
    int delta = Evaluate(score, a, occ, d, q) - score;
    if (delta >= 0) {
      Change(score, a, occ, d, q);
    }
    // temp *= cooling_rate;
  }
  if (Evaluate(ans) < Evaluate(a)) {
    ans = a;
  }
}

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

  Read();
  for (int rep = 0; rep < 10; rep++) {
    Solve();
  }
  Write();
  // cerr << Evaluate(ans) << "\n";
  return 0;
}


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

mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());

int N, D;
vector<int> C;
vector<vector<int>> S;

vector<int> ans;

void Read(bool local = false) {
  N = 26;
  if (local) {
    D = 365;
  } else {
    cin >> D;
  }
  C.resize(N);
  for (int i = 0; i < N; i++) {
    if (local) {
      C[i] = rnd() % 100;
    } else {
      cin >> C[i];
    }
  }
  S.resize(D);
  for (int i = 0; i < D; i++) {
    S[i].resize(N);
    for (int j = 0; j < N; j++) {
      if (local) {
        S[i][j] = rnd() % 20000;
      } else {
        cin >> S[i][j];
      }
    }
  }
  ans.assign(D, 0);
}

void Write() {
  for (auto i : ans) {
    cout << i + 1 << "\n";
  }
}

int Arithmetic(int n) { return n * (n - 1) / 2; }

vector<set<int>> Build(vector<int> a) {
  vector<set<int>> occ(N);
  for (int i = 0; i < D; i++) {
    occ[a[i]].insert(i);
  }
  for (int i = 0; i < N; i++) {
    occ[i].insert(-1);
    occ[i].insert(D);
  }
  return occ;
}

int Evaluate(vector<int> a) {
  vector<int> last(N, -1);
  int score = 0;
  for (int i = 0; i < D; i++) {
    score += S[i][a[i]];
    last[a[i]] = i;
    for (int j = 0; j < 26; j++) {
      score -= C[j] * (i - last[j]);
    }
  }
  return score;
}

int Evaluate(int init_score, const vector<int> &a, const vector<set<int>> &occ,
             int d, int q) {
  if (a[d] == q)
    return init_score;
  const set<int> &cur = occ[a[d]];
  auto pos = cur.lower_bound(d);
  int lst = *prev(pos);
  int nxt = *next(pos);

  int score = init_score;
  score += C[a[d]] *
           (Arithmetic(nxt - d) + Arithmetic(d - lst) - Arithmetic(nxt - lst));

  pos = occ[q].upper_bound(d);
  lst = *prev(pos);
  nxt = *pos;
  score -= C[q] *
           (Arithmetic(nxt - d) + Arithmetic(d - lst) - Arithmetic(nxt - lst));

  score -= S[d][a[d]];
  score += S[d][q];

  return score;
}

void Change(int &init_score, vector<int> &a, vector<set<int>> &occ, int d,
            int q) {
  int new_score = Evaluate(init_score, a, occ, d, q);
  init_score = new_score;
  occ[a[d]].erase(d);
  a[d] = q;
  occ[a[d]].insert(d);
}

void Solve() {
  vector<int> a(D);
  for (int i = 0; i < D; i++) {
    a[i] = rnd() % N;
  }
  int score = Evaluate(a);
  vector<set<int>> occ = Build(a);

  double temp = 10000;
  double cooling_rate = 0.999999;
  double absolute_zero = 0.00000001;
  int rep = 1e6;
  while (rep--) {
    int d = rnd() % D;
    int q = rnd() % N;
    int delta = Evaluate(score, a, occ, d, q) - score;
    if (delta >= 0) {
      Change(score, a, occ, d, q);
    }
    // temp *= cooling_rate;
  }
  if (Evaluate(ans) < Evaluate(a)) {
    ans = a;
  }
}

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

  Read();
  for (int rep = 0; rep < 10; rep++) {
    Solve();
  }
  Write();
  // cerr << Evaluate(ans) << "\n";
  return 0;
}