Submission #337612

#	Time	Username	Problem	Language	Result	Execution time	Memory
337612		ncduy0303	Discharging (NOI20_discharging)	C++17	100 / 100	156 ms	18656 KiB

Discharging

#include <bits/stdc++.h>

using namespace std;

#define ar array
#define ll long long

const int MAX_N = 1e5 + 1;
const ll MOD = 1e9 + 7;
const ll INF = 1e9;

struct convexhull {
    struct line {
        ll m, c; 
        line(ll m, ll c): m(m), c(c) {}
        ll operator()(ll x) {return m * x + c;}
    };
    deque<line> dq;
 
    bool bad(line a, line b, line c) {
        return 1.0 * (c.c - a.c) / (a.m - c.m) <= 1.0 * (b.c - a.c) /  (a.m - b.m);
    }
 
    void add(line l) {
        while(dq.size() > 1 && bad(dq[(int)dq.size() - 2], dq.back(), l))
            dq.pop_back();
        dq.emplace_back(l);
    }
 
    long query(long x) {
        if(dq.empty()) return 1e18;
        int l = 0, r = (int)dq.size() - 1;
        while(l < r) {
            int mid = (l + r) >> 1;
            if(dq[mid](x) >= dq[mid + 1](x))
                l = mid + 1;
            else r = mid;
        }
        return dq[r](x);
    }
};

void solve() {
    int n; cin >> n;
    vector<int> a(n + 1);
    for (int i = n; i > 0; i--) cin >> a[i];
    vector<int> st;
    for (int i = 1; i <= n; i++) {
        while (st.size() && a[st.back()] <= a[i]) st.pop_back();
        st.push_back(i);
    }
    int m = st.size();
    vector<ll> dp(m + 1);
    convexhull cht;
    for (int i = 1; i <= m; i++) {
        cht.add({a[st[i - 1]], dp[i - 1]});
        dp[i] = cht.query(st[i - 1]);
    }
    cout << dp[m] << "\n";
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    int tc = 1;
    // cin >> tc;
    for (int t = 1; t <= tc; t++) {
        // cout << "Case #" << t  << ": ";
        solve();
    }
}

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