Submission #659844

#	Time	Username	Problem	Language	Result	Execution time	Memory
659844		600Mihnea	Event Hopping (BOI22_events)	C++17	10 / 100	1592 ms	2644 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;
}

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;
  }
  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 L = ss, R = ss, cost = 0;
    while (L > ff) {
      int L2 = L, R2 = R;
      for (int j = L; j <= R; j++) {
        L2 = min(L2, low[j]);
        R2 = max(R2, high[j]);
      }
      if (L2 == L && R2 == R) {
        break;
      }
      L = L2;
      R = R2;
      cost++;
    }
    if (!(L <= ff && ff <= R)) {
      cout << "impossible\n";
    } else {
      cout << cost << "\n";
    }
  }

  return 0;
}
/**

**/

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:51:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |     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