Submission #1103852

#	Time	Username	Problem	Language	Result	Execution time	Memory
1103852		VinhLuu	Long Distance Coach (JOI17_coach)	C++17	0 / 100	27 ms	25424 KiB

coach

#include <bits/stdc++.h>
#define int long long
#define ll long long
#define all(vin) vin.begin(), vin.end()
using namespace std;

typedef tuple<ll,ll,ll> tp;
typedef pair<int,int> pii;
const int N = 1e6 + 5;
const int oo = 2e9;

int n, K, a[N], f[2][N], s[N];

vector<pii> hull;
int ptr = 0;

bool check(pii x, pii y, pii z){
  return 1.0 * (z.second - x.second) / 1.0 * (x.first - z.first) < 1.0 * (y.second - x.second) / 1.0 * (x.first - y.first);
//  return 1.0 * (z.second - y.second) / 1.0 * (y.first - z.first) > 1.0 * (y.second - x.second) / 1.0 * (x.first - y.first);
}

void add(pii x){
  while((int)hull.size() >= 2 && check(hull[(int)hull.size() - 2], hull.back(), x)) hull.pop_back();
  hull.push_back(x);
}

int get(pii x,int y){
  return x.first * y + x.second;
}

int query(int x){
  int l = 0, r = (int)hull.size() - 2, ans = get(hull.back(), x), pos = 0;
  while(l <= r){
    int mid = (l + r) / 2;
    if(get(hull[mid], x) >= get(hull[mid + 1], x)) pos = l = mid + 1;
    else r = mid - 1;
    ans = max({ans, get(hull[mid], x), get(hull[mid + 1], x)});
  }
  ans = min(ans, get(hull[pos], x));
  return ans;
}

namespace sub1{
  int dp[3005][3005];
  void pk(int &x,int y){
    if(x == -1) x = y;
    else x = min(x, y);
  }
  void solve(){
    memset(dp, -1, sizeof(dp));
    dp[0][0] = 0;
    for(int i = 1; i <= n; i ++){
      for(int j = 1; j <= min(i, K); j ++){
        for(int p = j - 1; p <= i - 1; p ++) if(dp[p][j - 1] != -1){
          pk(dp[i][j], dp[p][j - 1] + (s[i] - s[p]) * (s[i] - s[p]));
        }
      }
    }
    cout << dp[n][K];
  }
}

signed main(){
  ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  #define task "v"
  if(fopen(task ".inp","r")){
    freopen(task ".inp","r",stdin);
    freopen(task ".out","w",stdout);
  }
  cin >> n >> K;

  for(int i = 1; i <= n; i ++){
    cin >> a[i];
    s[i] = s[i - 1] + a[i];
  }


  int pre = 0, nx = 1;
  for(int i = 1; i <= n;i ++){
    f[0][i] = s[i] * s[i];
  }

  for(int k = 2; k <= K; k ++){
    hull.clear();
    ptr = 0;
    add({-2 * s[k - 1], s[k - 1] * s[k - 1] + f[pre][k - 1]});
    for(int i = k; i <= n; i ++){
      f[nx][i] = s[i] * s[i] + query(s[i]);
      add({-2 * s[i], s[i] * s[i] + f[pre][i]});
    }
    swap(pre, nx);
  }
  cout << f[pre][n];


}

Compilation message (stderr)

coach.cpp: In function 'int main()':
coach.cpp:67:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   67 |     freopen(task ".inp","r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
coach.cpp:68:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   68 |     freopen(task ".out","w",stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 16
• Subtask 2: 0 / 30
• Subtask 3: 0 / 25
• Subtask 4: 0 / 29