Submission #792093

#	Time	Username	Problem	Language	Result	Execution time	Memory
792093		peijar	Railway Trip (JOI17_railway_trip)	C++17	100 / 100	299 ms	34696 KiB

railway_trip

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

string to_string(string s) { return s; }
template <typename T> string to_string(T v) {
  bool first = true;
  string res = "[";
  for (const auto &x : v) {
    if (!first)
      res += ", ";
    first = false;
    res += to_string(x);
  }
  res += "]";
  return res;
}

void dbg_out() { cout << endl; }
template <typename Head, typename... Tail> void dbg_out(Head H, Tail... T) {
  cout << ' ' << to_string(H);
  dbg_out(T...);
}

#ifdef DEBUG
#define dbg(...) cout << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif

const int MAXN = 1e5;
const int MAXP = 20;

int goleft[MAXP][MAXN], goright[MAXP][MAXN];
int N, K, Q;

pair<int, int> advance(int L, int R, int p) {
  int nL, nR;
  if (L != -1)
    nL = goleft[p][L];
  else
    nL = -1;
  if (R != N)
    nL = min(nL, goleft[p][R]);
  if (R != N)
    nR = goright[p][R];
  else
    nR = N;
  if (L != -1)
    nR = max(nR, goright[p][L]);
  return pair(nL, nR);
}

signed main(void) {
  ios_base::sync_with_stdio(false);
  cin.tie(0);

  cin >> N >> K >> Q;

  vector<int> level(N);
  for (int &x : level)
    cin >> x;

  for (int i = 0; i < N; ++i) {
    int j = i - 1;
    while (j >= 0 and level[j] < level[i])
      j = goleft[0][j];

    goleft[0][i] = j;
  }

  for (int i = N - 1; i >= 0; --i) {
    int j = i + 1;
    while (j < N and level[j] < level[i])
      j = goright[0][j];
    goright[0][i] = j;
  }

  for (int p = 0; p < MAXP - 1; ++p)
    for (int i = 0; i < N; ++i) {
      int L = goleft[p][i];
      int R = goright[p][i];
      if (L != -1)
        goleft[p + 1][i] = goleft[p][L];
      else
        goleft[p + 1][i] = -1;
      if (R != N)
        goleft[p + 1][i] = min(goleft[p + 1][i], goleft[p][R]);
      if (R != N)
        goright[p + 1][i] = goright[p][R];
      else
        goright[p + 1][i] = N;
      if (L != -1)
        goright[p + 1][i] = max(goright[p + 1][i], goright[p][L]);
    }

  while (Q--) {
    int A, B;
    cin >> A >> B;
    --A, --B;
    if (A > B)
      swap(A, B);
    int sol = 0;
    int LA = A, RA = A;

    /*while (advance(LA, RA, 0).second <= B) {
      sol++;
      tie(LA, RA) = advance(LA, RA, 0);
    }
    int LB = B, RB = B;
    while (advance(LB, RB, 0).first >= RA) {
      sol++;
      tie(LB, RB) = advance(LB, RB, 0);
    }*/
    for (int p = MAXP - 1; p >= 0; --p)
      if (advance(LA, RA, p).second <= B) {
        sol += 1 << p;
        tie(LA, RA) = advance(LA, RA, p);
      }

    int LB = B, RB = B;
    for (int p = MAXP - 1; p >= 0; --p)
      if (advance(LB, RB, p).first >= RA) {
        sol += 1 << p;
        tie(LB, RB) = advance(LB, RB, p);
      }

    if (RA < LB)
      sol++;
    cout << sol - 1 << '\n';
  }
}

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 25 / 25
• Subtask 4: 55 / 55