제출 #994795

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
994795		12345678	Chorus (JOI23_chorus)	C++17	100 / 100	1839 ms	55668 KiB

chorus

#include <bits/stdc++.h>

using namespace std;

const int nx=1e6+5;

#define ll long long

ll n, k, h[nx], p[nx], qs[nx], r=0, c=1, idx=1;
pair<ll, ll> dp[nx];
string s;

struct line
{
    ll m, c, cnt;
    line(ll m=0, ll c=0, ll cnt=0): m(m), c(c), cnt(cnt){}
    ll val(ll x) {return m*x+c;}
};

struct convexhulltrick
{
    deque<line> dq;
    ll bad(line a, line b, line c)
    {
        return (a.c-c.c)*(b.m-a.m)<(a.c-b.c)*(c.m-a.m);
    }
    void add(line x)
    {
        while (dq.size()>=2&&bad(dq[dq.size()-2], dq.back(), x)) dq.pop_back();
        dq.push_back(x);
    }
    line query(ll x)
    {
        while (dq.size()>=2&&dq[0].val(x)>dq[1].val(x)) dq.pop_front();
        return dq[0];
    }
} d;

pair<ll, ll> solve(ll lambda)
{
    idx=1;
    d.dq.clear();
    for (int i=1; i<=n; i++)
    {
        while (idx<=p[i]&&idx<=i) d.add(line(-idx, qs[idx-1]+dp[idx-1].first, dp[idx-1].second)), idx++;
        dp[i]={d.query(i).val(i)+i*p[i]-qs[p[i]-1]+lambda, d.query(i).cnt+1};
    }
    return dp[n];
}

int main()
{
    cin.tie(NULL)->sync_with_stdio(false);
    cin>>n>>k>>s;
    for (int i=0; i<2*n; i++)
    {
        if (s[i]=='A') r++, h[c]=r;
        if (s[i]=='B') c++, h[c]=r;
    }
    for (int i=1; i<=n; i++)
    {
        qs[i]=qs[i-1]+h[i];
        while (idx<=i&&h[idx]<i) idx++;
        p[i]=idx;
    }
    /*
    cout<<"debug "<<1<<'\n';
    solve(1);
    for (int i=1; i<=n; i++) cout<<i<<' '<<dp[i].first<<' '<<dp[i].second<<'\n';
    for (auto x:d.dq) cout<<"dq "<<x.m<<' '<<x.c<<' '<<x.cnt<<'\n';*/
    ll l=0, r=1e12;
    while (l<r)
    {
        ll md=(l+r)/2;
        if (solve(md).second<=k) r=md;
        else l=md+1;
    }
    cout<<solve(l).first-k*l;
}

/*
(a.c-c.c)/(c.m-a.m)<(a.c-b.c)/(b.m-a.m)
*/

• Subtask 1: 16 / 16
• Subtask 2: 24 / 24
• Subtask 3: 21 / 21
• Subtask 4: 26 / 26
• Subtask 5: 13 / 13