Submission #256907

#	Time	Username	Problem	Language	Result	Execution time	Memory
256907		Bruteforceman	Discharging (NOI20_discharging)	C++11	13 / 100	1107 ms	353716 KiB

Discharging

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e6 + 10;
const long long inf = 1e16;
long long dp[maxn];
int a[maxn];
int n;

struct hull {
  vector <long long> M, C;
  int pt = 0;
  bool bad(int i, int j, int k) {
    return (C[k] - C[j]) * (M[i] - M[k]) <= (C[k] - C[i]) * (M[j] - M[k]);
  }
  void add(long long m, long long c) {
    M.push_back(m);
    C.push_back(c);
    while(M.size() >= 3 && bad(M.size() - 3, M.size() - 2, M.size() - 1)) {
      M.erase(M.end() - 2);
      C.erase(C.end() - 2);
    }
  }
  long long eval(long long x) {
    while(pt + 1 < M.size() && 
        M[pt] * x + C[pt] >= M[pt + 1] * x + C[pt + 1]) {
      ++pt;
    }
    return M[pt] * x + C[pt];
  }
} t[maxn * 4];
void update(int x, int c = 1, int b = 1, int e = n) {
  t[c].add(n - x, dp[x]);
  if(b == e) {
    return ;
  }
  int m = (b + e) >> 1;
  int l = c << 1;
  int r = l + 1;
  if(x <= m) update(x, l, b, m);
  else update(x, r, m + 1, e);
}
long long query(int x, int y, int val, int c = 1, int b = 1, int e = n) {
  if(x <= b && e <= y) {
    return t[c].eval(val);
  }
  if(y < b || e < x) return inf;
  int m = (b + e) >> 1;
  int l = c << 1;
  int r = l + 1;
  return min(query(x, y, val, l, b, m), query(x, y, val, r, m + 1, e));
}
int main() {
  scanf("%d", &n);
  for(int i = 1; i <= n; i++) scanf("%d", &a[i]);
  vector <int> v ({0});
  a[0] = INT_MAX;
  update(0);
  dp[0] = inf;
  for(int i = 1; i <= n; i++) {
    while(a[v.back()] <= a[i]) {
      v.pop_back();
    }
    dp[i] = min(dp[v.back()], query(v.back(), i - 1, a[i]));
    update(i);
    v.push_back(i);
  }
  printf("%lld\n", dp[n]);
  return 0;
}

Compilation message (stderr)

Discharging.cpp: In member function 'long long int hull::eval(long long int)':
Discharging.cpp:24:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     while(pt + 1 < M.size() && 
           ~~~~~~~^~~~~~~~~~
Discharging.cpp: In function 'int main()':
Discharging.cpp:53:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &n);
   ~~~~~^~~~~~~~~~
Discharging.cpp:54:36: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   for(int i = 1; i <= n; i++) scanf("%d", &a[i]);
                               ~~~~~^~~~~~~~~~~~~

• Subtask 1: 0 / 9
• Subtask 2: 13 / 13
• Subtask 3: 0 / 25
• Subtask 4: 0 / 11
• Subtask 5: 0 / 14
• Subtask 6: 0 / 28