Submission #691312

#	Time	Username	Problem	Language	Result	Execution time	Memory
691312		saayan007	Discharging (NOI20_discharging)	C++17	100 / 100	147 ms	33448 KiB

Discharging

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

using ll = long long;
using pi = pair<int, int>;
using pl = pair<long long, long long>;
using vi = vector<int>;
using vl = vector<long long>;
using vpi = vector<pair<int, int>>;
using vpl = vector<pair<long long, long long>>;

#define fur(i, a, b) for(ll i = a; i <= (ll)b; ++i)
#define ruf(i, a, b) for(ll i = a; i >= (ll)b; --i)
#define fr first 
#define sc second
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define nl "\n"
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()

const ll inf = 1e16L;
struct CHT {
    struct Line {
        ll m, c;

        Line(ll a, ll b){
            m = a;
            c = b;
        }

        ll isect(Line &other) {
            return (c - other.c + other.m - m + 1) / (other.m - m);
        }

        ll val(ll x) {
            return m*x + c;
        }
    };

    deque<pair<Line, ll>> dq;

    void insert(ll m, ll c) {
        Line nex(m, c);
        if(dq.empty()) {
            dq.eb(nex, 0);
            return;
        }

        while(!dq.empty()) {
            Line pr = dq.back().fr;
            ll x = dq.back().sc;
            if(nex.m == pr.m) {
                if(nex.c > pr.c) {
                    return;
                }
            } else if(nex.isect(pr) > x) {
                break;
            }
            dq.pop_back();
        }

        if(dq.empty()) {
            dq.eb(nex, 0);
            return;
        }

        dq.eb(nex, nex.isect(dq.back().fr));
    }

    ll query(ll x) {
        ll m = dq.size();
        while(m > 1 && dq[1].sc <= x) {
            dq.pop_front();
            --m;
        }
        return dq.front().fr.val(x);
    }
};

int main() 
{
    ios::sync_with_stdio(0);
    cin.tie(0);

    ll n;
    cin >> n;

    ll t[n + 1];
    fur(i, 1, n)
        cin >> t[i];

    ll dp[n + 1];
    dp[0] = 0;
    ll p[n + 1];
    p[1] = 1;

    fur(i, 2, n) {
        if(t[i] > t[p[i - 1]])
            p[i] = i;
        else p[i] = p[i - 1];
    }

    CHT cht;
    fur(i, 1, n) {
        cht.insert(n - i + 1, dp[i - 1]);
        dp[i] = cht.query(t[p[i]]);
    }

    cout << dp[n] << nl;
}

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