Submission #1029389

#	Time	Username	Problem	Language	Result	Execution time	Memory
1029389		MDario	The short shank; Redemption (BOI21_prison)	C++17	10 / 100	49 ms	20164 KiB

prison

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

#define F first
#define S second
typedef long long ll;

const string noyes[2] = {"NO", "YES"};
const ll INFLL = (1ll << 62);
const int INF = (1 << 30);
const int MAXN = 2'000'000;
const ll MOD = 1'000'000'007;

ll n, D, T;
ll a[MAXN];
int dp[MAXN][2];

void subtask_1() {
  {
    int c = 0;
    ll last = INF;
    for (int i = 0; i < n; i++) {
      last = min(last + 1, a[i]);
      c += (last <= T);
      dp[i][0] = c;
    }
  }
  for (int i = 0; i < D; i++) {
    int cur = i & 1;
    for (int t = i; t < n; t++)
      dp[t][cur ^ 1] = INF;
    for (int t = i; t < n; t++) {
      int c = 0;
      ll last = INF;
      for (int e = t + 1; e < n; e++) {
        last = min(last + 1, a[e]);
        c += (last <= T);
        dp[e][cur ^ 1] = min(dp[e][cur ^ 1], dp[t][cur] + c);
      }
    }
  }

  cout << dp[n - 1][D & 1] << "\n";
}

void subtask_2() {
  ll pref[n];
  {
    ll c = 0;
    ll last = INF;
    for (int i = 0; i < n; i++) {
      last = min(last + 1, a[i]);
      if (last <= T) {
        c++;
      }
      pref[i] = c;
    }
  }

  ll suf[n];
  {
    stack<ll> slow;
    ll c = 0;
    ll last = INF;
    for (int i = n - 1; i >= 0; i--) {
      last = a[i];
      slow.push(i);
      while (!slow.empty() && abs(i - slow.top()) + last <= T) {
        c++;
        slow.pop();
      }
      suf[i] = c;
    }
  }

  ll ans = n;
  for (int i = 0; i + 1 < n; i++)
    ans = min(ans, pref[i] + suf[i + 1]);
  cout << ans << "\n";
  return;
}

void subtask_3_4() {
  pair<int, int> f[n];
  {
    stack<int> s;
    for (int i = n - 1; i >= 0; i--) {
      f[i] = {-1, n};
      int c = 0;
      s.push(a[i]);
      while (!s.empty() && abs(i - s.top()) + a[i] <= T) {
        c++;
        f[s.top()] = {i, s.top() - i - c};
        s.pop();
      }
    }
  }
  {
    int c = 0;
    ll last = INF;
    for (int i = 0; i < n; i++) {
      last = min(last + 1, a[i]);
      c += (last <= T);
      dp[i][0] = c;
    }
  }
  for (int i = 0; i < D; i++) {
    int cur = i & 1;
    int p = i;
    dp[i + 1][cur ^ 1] = dp[i][cur] + (a[i + 1] <= T);
    for (int t = i + 2; t < n; t++) {
      dp[t][cur ^ 1] = dp[t - 1][cur ^ 1] + (f[t].F > p);
      if (f[t].F > p) {
        if (dp[t][cur ^ 1] > (dp[f[t].F][cur] + f[t].S)) {
          p = f[t].F;
          dp[t][cur ^ 1] = (dp[f[t].F][cur] + f[t].S);
        }
      }
    }
  }

  cout << dp[n - 1][D & 1] << "\n";
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  cin >> n >> D >> T;

  for (int i = 0; i < n; i++)
    cin >> a[i];

  if (D == 1)
    subtask_2();
  else
    subtask_3_4();

  return 0;
}

• Subtask 1: 0 / 15
• Subtask 2: 10 / 10
• Subtask 3: 0 / 20
• Subtask 4: 0 / 10
• Subtask 5: 0 / 25
• Subtask 6: 0 / 20