Submission #881809

#	Time	Username	Problem	Language	Result	Execution time	Memory
881809		npmduyy	Building Bridges (CEOI17_building)	C++14	100 / 100	38 ms	9676 KiB

building

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

typedef long long ll;
const int maxN = 1e5;

struct Line {
    mutable ll k, m, p;
    bool operator<(const Line& o) const { return k < o.k; }
    bool operator<(ll x) const { return p < x; }
};

struct LineContainer : multiset<Line, less<>> {
    // (for doubles, use inf = 1/.0, div(a,b) = a/b)
    static const ll inf = LLONG_MAX;
    ll div(ll a, ll b) { // floored division
        return a / b - ((a ^ b) < 0 && a % b);
    }
    bool isect(iterator x, iterator y) {
        if (y == end()) return x->p = inf, 0;
        if (x->k == y->k) x->p = x->m > y->m ? inf : -inf;
        else x->p = div(y->m - x->m, x->k - y->k);
        return x->p >= y->p;
    }
    void add(ll k, ll m) {
        auto z = insert({k, m, 0}), y = z++, x = y;
        while (isect(y, z)) z = erase(z);
        if (x != begin() && isect(--x, y)) isect(x, y = erase(y));
        while ((y = x) != begin() && (--x)->p >= y->p)
            isect(x, erase(y));
    }
    ll query(ll x) {
        assert(!empty());
        auto l = *lower_bound(x);
        return l.k * x + l.m;
    }
};

int n;
ll h[maxN+1], w[maxN+1], dp[maxN+1];

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    cin >> n;
    for (int i = 1; i <= n; ++i) {
        cin >> h[i];
    }
    for (int i = 1; i <= n; ++i) {
        cin >> w[i];
        w[i] += w[i-1];
    }

    LineContainer hull;
    hull.add(h[1]*2, - h[1]*h[1] + w[1]);
    for (int i = 2; i <= n; ++i) {
        dp[i] = w[i-1] + h[i]*h[i] - hull.query(h[i]);
        hull.add(h[i]*2, - h[i]*h[i] + w[i] - dp[i]);
    }
    cout << dp[n];
}

• Subtask 1: 30 / 30
• Subtask 2: 30 / 30
• Subtask 3: 40 / 40