Submission #261330

#	Time	Username	Problem	Language	Result	Execution time	Memory
261330		Nightlight	Discharging (NOI20_discharging)	C++14	100 / 100	248 ms	30052 KiB

Discharging

#include <bits/stdc++.h>
#define pii pair<long long, long long>
#define inter second
#define slope first
using namespace std;

int N;
long long A[1000005], ans = LLONG_MAX;
long long T[1000005];
long long pos[1000005];
long long dp[1000005];
pii CHT[100005];
int sz, pointer;
int p;

inline double isect(pii a, pii b) {return (a.inter - b.inter) / (b.slope - a.slope);}
inline bool bad(pii a, pii b, pii c) {return isect(c, a) < isect(a, b);}
inline long long val(long long X, int id) {return CHT[id].slope * X + CHT[id].inter;}

void insert(long long m, long long b) {
  pii L = {m, b};
  while(sz > 1 && bad(CHT[sz - 1], CHT[sz], L)) sz--;
  CHT[++sz] = L;
}

long long query(long long X) {
  long long res = LLONG_MAX;
//  cout << X << "\n";
  for(int i = 1; i <= sz; i++) {
    res = min(res, val(X, i));
//    cout << CHT[i].first << ": " << val(X, i) << "\n";
  }
//  cout << "\n";
  return res;
}

int main() {
  scanf("%d", &N);
  for(int i = 1; i <= N; i++) {
    scanf("%lld", &T[i]);
    if(T[i] > A[p]) {
      A[++p] = T[i];
      pos[p] = i;
    }
  }
  dp[p] = A[p] * (N - pos[p] + 1);
  ans = A[p] * N;
  insert(A[p], dp[p] + A[p] * pos[p]);
  for(int i = p - 1; i > 0; i--) {
    dp[i] = A[i] * (N - pos[i] + 1) + query(-pos[i + 1]);
    insert(A[i], dp[i] + A[i] * pos[i]);
    ans = min(ans, dp[i] + A[i] * (pos[i] - 1));    
  }
  printf("%lld\n", ans);
  cin >> N;
}

Compilation message (stderr)

Discharging.cpp: In function 'int main()':
Discharging.cpp:38:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &N);
   ~~~~~^~~~~~~~~~
Discharging.cpp:40:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lld", &T[i]);
     ~~~~~^~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 13 / 13
• Subtask 3: 25 / 25
• Subtask 4: 11 / 11
• Subtask 5: 14 / 14
• Subtask 6: 28 / 28