Submission #426929

#	Time	Username	Problem	Language	Result	Execution time	Memory
426929		egekabas	Discharging (NOI20_discharging)	C++14	100 / 100	216 ms	34356 KiB

Discharging

#include <bits/stdc++.h>
#define all(x) (x).begin(), (x).end()
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pull;
typedef pair<int, int> pii;
typedef pair<ld, ld> pld;
ll n, a[1000009];
struct line{
    ll a, b;
    ll get(ll x){
        return a*x+b;
    }
};
ld inter(line x, line y){
    return ld(y.b-x.b)/ld(x.a-y.a);
}
vector<line> vec;
void add(line x){
    while(vec.size() >= 2){
        if(inter(vec[vec.size()-2], x) <= inter(vec[vec.size()-2], vec.back()))
            vec.pop_back();
        else
            break;
    }
    vec.pb(x);
}
ll get(ll lim, ll x){
    ll l = 0, r = vec.size()-1;
    while(l < r){
        ll m = (l+r)/2;
        if(-vec[m].a < lim || vec[m+1].get(x) < vec[m].get(x))
            l = m+1;
        else
            r = m;
    }
    return vec[l].get(x);
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);

    cin >> n;
    for(ll i = 1; i <= n; ++i)
        cin >> a[i];
    a[0] = -1;
    add({0, 0});
    vector<pll> bigs;
    bigs.pb({0, 0});
    for(ll i = 1; i <= n; ++i){
        while(bigs.size() && a[bigs.back().ff] <= a[i]){
            bigs.pop_back();
        }
        ll lim = 0;
        ll dp = 1e18;
        if(bigs.size()){
            lim = bigs.back().ff;
            dp = bigs.back().ss;
        }
        
        dp = min(get(lim, a[i])+a[i]*n, dp);
        add({-i, dp});
        bigs.pb({i, dp});
    }
    cout << bigs.back().ss << '\n';
}

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