Submission #659846

#	Time	Username	Problem	Language	Result	Execution time	Memory
659846		600Mihnea	Event Hopping (BOI22_events)	C++17	10 / 100	1589 ms	59448 KiB

events

bool home = 0;
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
const int N = (int) 1e5 + 7;
int n;
int q;

struct T {
  int l;
  int r;
  int init;
};

bool operator < (T a, T b) {
  if (a.r != b.r) {
    return a.r < b.r;
  } else {
    return a.l < b.l;
  }
}

T v[N];
int dp[N];
int nxt[N];
int ant[N];
int inv[N];
int low[N];
int high[N];

int cnt_rs_under(int limit) {
  int low = 1, high = n, cnt = 0;
  while (low <= high) {
    int mid = (low + high) / 2;
    if (v[mid].r <= limit) {
      cnt = mid;
      low = mid + 1;
    } else {
      high = mid - 1;
    }
  }
  return cnt;
}

pair<int, int> join(pair<int, int> a, pair<int, int> b) {
  return {min(a.first, b.first), max(a.second, b.second)};
}

const int K = 20;
const int INF = (int) 1e9 + 7;
pair<int, int> after[K][N];
pair<int, int> tree[K][4 * N];

void build(int v, int tl, int tr, int k) {
  if (tl == tr) {
    tree[k][v] = after[k][tl];
  } else {
    int tm = (tl + tr) / 2;
    build(2 * v, tl, tm, k);
    build(2 * v + 1, tm + 1, tr, k);
    tree[k][v] = join(tree[k][2 * v], tree[k][2 * v + 1]);
  }
}

pair<int, int> get(int v, int tl, int tr, int l, int r, int k) {
  if (tr < l || r < tl) {
    return make_pair(INF, -INF);
  }
  if (l <= tl && tr <= r) {
    return tree[k][v];
  }
  int tm = (tl + tr) / 2;
  return join(get(2 * v, tl, tm, l, r, k), get(2 * v + 1, tm + 1, tr, l, r, k));
}

pair<int, int> get(int l, int r, int k) {
  return get(1, 1, n, l, r, k);
}

void build(int k) {
  build(1, 1, n, k);
}

pair<int, int> do_2_pw_k_steps(pair<int, int> cur, int k) {
  int L = cur.first, R = cur.second;
  assert(1 <= L && L <= R && R <= n);
  return get(L, R, k);
}

int main() {
  if (!home) {
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  } else {
    freopen("input.txt", "r", stdin);
  }

  cin >> n >> q;
  for (int i = 1; i <= n; i++) {
    cin >> v[i].l >> v[i].r;
    v[i].init = i;
  }
  sort(v + 1, v + n + 1);
  for (int i = 1; i <= n; i++) {
    int x = cnt_rs_under(v[i].l - 1) + 1;
    int y = cnt_rs_under(v[i].r);
    low[i] = x;
    high[i] = y;
    after[0][i] = {low[i], high[i]};
  }
  build(0);
  for (int k = 1; k < K; k++) {
    for (int i = 1; i <= n; i++) {
      after[k][i] = do_2_pw_k_steps(after[k - 1][i], k - 1);
    }
    build(k);
  }
  for (int i = 1; i <= n; i++) {
    inv[v[i].init] = i;
  }

  for (int iq = 1; iq <= q; iq++) {
    int ff, ss;
    cin >> ff >> ss;
    ff = inv[ff];
    ss = inv[ss];
    int cost = 0;
    pair<int, int> cur = {ss, ss};
    {
      pair<int, int> nxt_cur = do_2_pw_k_steps(cur, K - 1);
      if (!(nxt_cur.first <= ff && ff <= nxt_cur.second)) {
        cout << "impossible\n";
        continue;
      }
    }
    while (!(cur.first <= ff && ff <= cur.second)) {
      cur = do_2_pw_k_steps(cur, 0);
      cost++;
    }
    cout << cost << "\n";
  }

  return 0;
}
/**

**/

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:96:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   96 |     freopen("input.txt", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 10 / 10
• Subtask 3: 0 / 15
• Subtask 4: 0 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30