Submission #1079437

#	Time	Username	Problem	Language	Result	Execution time	Memory
1079437		12345678	Building Bridges (CEOI17_building)	C++17	100 / 100	50 ms	9680 KiB

building

#include <bits/stdc++.h>

using namespace std;

#define ll long long

const ll nx=1e5+5, inf=1e18;

ll n, h[nx], w[nx], sm, dp[nx];
bool querymode;

struct line
{
    ll m, c;
    mutable ll p;
    line(ll m=0, ll c=0, ll p=0): m(m), c(c), p(p){}
    bool operator<(const line &o) const {return querymode?p<o.p:m>o.m;}
};

struct convexhulltrick:multiset<line>
{
    ll div(ll a, ll b)
    {
        if ((a%b)==0||((a^b)>0)) return a/b;
        return a/b-1;
    }
    bool isect(iterator x, iterator y)
    {
        if (y==end()) return x->p=inf, 0;
        if (x->m==y->m) x->p=(x->c<=y->c)?inf:-inf;
        else x->p=div(y->c-x->c, x->m-y->m);
        return x->p>=y->p;
    }
    void add(line l)
    {
        auto x=insert(l), y=next(x);
        while (isect(x, y)) y=erase(y);
        while ((y=x)!=begin()&&isect(--x, y)) isect(x, erase(y));
        while ((y=x)!=begin()&&isect(--x, y)) isect(x, erase(y));
    }
    ll query(ll x)
    {
        querymode=1;
        auto itr=lower_bound(line(0, 0, x));
        querymode=0;
        return itr->m*x+itr->c;
    }
} c;

int main()
{
    cin.tie(NULL)->sync_with_stdio(false);
    cin>>n;
    for (int i=1; i<=n; i++) cin>>h[i];
    for (int i=1; i<=n; i++) cin>>w[i], sm+=w[i];
    dp[1]=-w[1];
    c.add(line(-2*h[1], dp[1]+h[1]*h[1]));
    for (int i=2; i<=n; i++)
    {
        dp[i]=c.query(h[i])+h[i]*h[i]-w[i];
        c.add(line(-2*h[i], dp[i]+h[i]*h[i]));
        //cout<<"debug "<<i<<' '<<dp[i]<<'\n';
    }
    cout<<sm+dp[n];
}

/*
6
3 8 7 1 6 6
0 -1 9 1 2 0
*/

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