Submission #575196

#	Time	Username	Problem	Language	Result	Execution time	Memory
575196		JovanB	Discharging (NOI20_discharging)	C++17	100 / 100	472 ms	319876 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; }
} seg[4*N+5];
 
ll query(int node, int l, int r, int i){
    ll g = seg[node].eval(i);
    if(l == r) return g;
    int mid = (l+r)/2;
    if(i <= mid) return min(g, query(node*2, l, mid, i));
    return min(g, query(node*2+1, mid+1, r, i));
}
 
stack <tuple <line, int, int>> rev;
 
void brisi(int i){
    while(!rev.empty() && get<2>(rev.top()) == i){
        seg[get<1>(rev.top())] = get<0>(rev.top());
        rev.pop();
    }
}
 
void upd(int node, int l, int r, line g, int i){
    int mid = (l+r)/2;
    if(g.eval(mid) < seg[node].eval(mid)){
        rev.push({seg[node], node, i});
        swap(g, seg[node]);
    }
    if(l == r) return;
    if(seg[node].eval(l) > g.eval(l)) upd(node*2, l, mid, g, i);
    else upd(node*2+1, mid+1, r, g, i);
}
 
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);
    for(int i=1; i<=4*n; i++) seg[i].n = INF;
    stack <int> st;
    for(int i=1; i<=n; i++){
        while(!st.empty() && a[st.top()] <= a[i]){
            brisi(st.top());
            st.pop();
        }
        line h;
        h.k = a[i];
        h.n = 0;
        if(!st.empty()){
            h.n = dp[st.top()];
        }
        upd(1, 1, n, h, i);
        st.push(i);
        dp[i] = query(1, 1, n, i);
    }
    cout << dp[n] << "\n";
    return 0;
}

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