Submission #976611

#	Time	Username	Problem	Language	Result	Execution time	Memory
976611		0x34c	Building Bridges (CEOI17_building)	C++17	100 / 100	39 ms	9936 KiB

building

#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define endl '\n'
#define int ll

using namespace std;

const int INF = 1e13;

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) {
        k *= -1; m *= -1;
		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 -1*(l.k * x + l.m);
	}
};

signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int N;
    cin >> N;
    
    vector<int> pillars(N);
    vector<int> psum(N + 1, 0);
    for(int i = 0; i < N; i++) {
        cin >> pillars[i];
    }

    for(int i = 1; i <= N; i++) {
        cin >> psum[i];
        psum[i] += psum[i - 1];
    }

    LineContainer cht;
    vector<int> dp(N);
    cht.add(-2*pillars[0], pillars[0]*pillars[0] - psum[1]);

    for(int i = 1; i < N; i++) {
        dp[i] = dp[0] + (pillars[i] - pillars[0])*(pillars[i] - pillars[0]) + psum[i] - psum[1];
        dp[i] = pillars[i]*pillars[i] + psum[i] + cht.query(pillars[i]);
        cht.add(-2*pillars[i], pillars[i]*pillars[i] - psum[i + 1] + dp[i]);
    }

    cout << dp[N - 1] << endl;
}

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