Submission #962926

#	Time	Username	Problem	Language	Result	Execution time	Memory
962926		nguyentunglam	Shortcut (IOI16_shortcut)	C++17	38 / 100	2096 ms	117480 KiB

shortcut

#include<bits/stdc++.h>
using namespace std;
#include "shortcut.h"

const int N = 3e3 + 10;

long long f[N][N], g[N][N];

long long pref[N], suff[N], pref_mx[N], suff_mx[N], pref_l[N];

int pre[N];

long long find_shortcut(int n, std::vector<int> L, std::vector<int> d, int c)
{
  assert(f[0][1] == 0);
  pref[0] = d[0];
  suff[n - 1] = d[n - 1];
  for(int i = 1; i < n; i++) {
    pref[i] = max(pref[i - 1] + L[i - 1], (long long) d[i]);
    pref_mx[i] = max(pref_mx[i - 1], pref[i - 1] + L[i - 1] + d[i]);
  }
  for(int i = n - 2; i >= 0; i--) {
    suff[i] = max(suff[i + 1] + L[i], (long long) d[i]);
    suff_mx[i] = max(suff_mx[i + 1], suff[i + 1] + L[i] + d[i]);
  }

  for(int i = 1; i < n; i++) {
    pref_l[i] = pref_l[i - 1] + L[i - 1];
  }

  for(int x = 0; x < n; x++) {
    priority_queue<pair<long long, long long> > q;
    long long mx = 0;
    for(int y = x; y < n; y++) {
      q.push({d[y] - pref_l[y], d[y] + pref_l[y] - pref_l[x] + c});
      while (!q.empty()) {
        long long a, b; tie(a, b) = q.top();
        if (a + pref_l[y] >= b) {
          mx = max(mx, b);
          q.pop();
        }
        else {
          mx = max(mx, a + pref_l[y]);
          break;
        }
      }
      f[x][y] = mx;
    }
  }


  for(int x = n - 1; x >= 0; x--) {
    priority_queue<pair<long long, long long> > q;
    long long mx = 0;
    for(int y = x; y >= 0; y--) {
      q.push({d[y] + pref_l[y], d[y] + pref_l[x] - pref_l[y] + c});
      while (!q.empty()) {
        long long a, b; tie(a, b) = q.top();
        if (a - pref_l[y] >= b) {
          mx = max(mx, b);
          q.pop();
        }
        else {
          mx = max(mx, a - pref_l[y]);
          break;
        }
      }
      f[x][y] = mx;
    }
  }

//  cout << f[3][1] << endl;
  long long l = 0, r = 1e18, ans = -1;

  auto check = [&] (long long mid) {
    for(int i = n - 1; i >= 0; i--) for(int j = i; j < n; j++) {
      g[i][j] = max(g[i + 1][j], g[i][j - 1]);
      if (i == j) g[i][j] = -1e18;
      else if (pref_l[j] - pref_l[i] + d[i] + d[j] >= mid) {
//        cout << i << " " << j << endl;
        g[i][j] = max(g[i][j], d[i] + d[j] - pref_l[j] + pref_l[i]);
      }
    }
//    cout << f[1][2] << endl;
//    for(int i = 0; i < n; i++) cout << pre[i] << " "; cout << endl;
    long long best = 1e18;
    for(int x = 0; x < n; x++) {
      for(int y = x + 1; y < n; y++) {
        long long cost = max(pref_mx[x], suff_mx[y]);
        cost = max(cost, pref[x] + suff[y] + min((long long) c, pref_l[y] - pref_l[x]));
        if (y + 1 < n) cost = max(cost, f[x][y] + suff[y + 1] + L[y]);
        if (x - 1 >= 0) cost = max(cost, f[y][x] + pref[x - 1] + L[x - 1]);
        cost = max(cost, g[x][y] + c + pref_l[y] - pref_l[x]);
        best = min(best, cost);
//        cout << x << " " << y << " " << cost << " " << endl;
      }
    }
    return (best >= mid);
  };

//  cout << check(18);
//  exit(0);

  while (l <= r) {
    long long mid = l + r >> 1;
    if (check(mid)) {
      ans = mid;
      l = mid + 1;
    } else r = mid - 1;
  }
  return ans;
}

#ifdef ngu
int main()
{
  freopen ("task.inp", "r", stdin);
  freopen ("task.out", "w", stdout);
    int n, c;
    assert(2 == scanf("%d%d", &n, &c));

    std::vector<int> l(n - 1);
    std::vector<int> d(n);
    for (int i = 0; i < n - 1; i++)
        assert(1 == scanf("%d", &l[i]));
    for (int i = 0; i < n; i++)
        assert(1 == scanf("%d", &d[i]));

    long long t = find_shortcut(n, l, d, c);


    printf("%lld\n", t);

    return 0;
}
#endif // ngu

Compilation message (stderr)

shortcut.cpp: In function 'long long int find_shortcut(int, std::vector<int>, std::vector<int>, int)':
shortcut.cpp:105:23: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  105 |     long long mid = l + r >> 1;
      |                     ~~^~~

• Subtask 1: 9 / 9
• Subtask 2: 14 / 14
• Subtask 3: 8 / 8
• Subtask 4: 7 / 7
• Subtask 5: 0 / 33
• Subtask 6: 0 / 22
• Subtask 7: 0 / 4
• Subtask 8: 0 / 3