Submission #575907

#	Time	Username	Problem	Language	Result	Execution time	Memory
575907		JovanB	Discharging (NOI20_discharging)	C++17	100 / 100	114 ms	19244 KiB

Discharging

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

using ll = long long;
using ld = long double;

const int N = 1000000;
const ll INF = 1000000000000000000LL;

ll a[N+5];
ll dp[N+5];

struct line{
    ll k, n;
    ll eval(int x){ return k*x + n; }
    ld intersect(line h){
        return (ld)(n - h.n)/(h.k - k);
    }
};

deque <line> dq;

void dodaj(line g){
    while(dq.size() >= 2){
        line b = dq.back();
        dq.pop_back();
        line a = dq.back();
        dq.pop_back();
        if(a.intersect(g) > a.intersect(b)){
            dq.push_back(a);
            dq.push_back(b);
            break;
        }
        dq.push_back(a);
    }
    dq.push_back(g);
}

ll query(int x){
    while(dq.size() >= 2 && dq[0].eval(x) >= dq[1].eval(x)) dq.pop_front();
    return dq.front().eval(x);
}

int main(){
    ios_base::sync_with_stdio(false), cin.tie(0);
    cout.precision(10);
    cout << fixed;

    int n;
    cin >> n;
    for(int i=1; i<=n; i++){
        cin >> a[i];
    }
    reverse(a+1, a+1+n);
    vector <pair <int, int>> vec;
    for(int i=n; i>=1; i--){
        if(vec.empty() || vec.back().second < a[i]){
            vec.push_back({i, a[i]});
        }
    }
    reverse(vec.begin(), vec.end());
    for(int i=0; i<vec.size(); i++){
        int id, h;
        tie(id, h) = vec[i];
        line g;
        g.k = a[id];
        g.n = 0;
        if(i) g.n = dp[i-1];
        dodaj(g);
        dp[i] = query(id);
    }
    cout << dp[vec.size() - 1] << "\n";
    return 0;
}

Compilation message (stderr)

Discharging.cpp: In function 'int main()':
Discharging.cpp:62:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   62 |     for(int i=0; i<vec.size(); 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