Submission #953475

#	Time	Username	Problem	Language	Result	Execution time	Memory
953475		owoovo	Chorus (JOI23_chorus)	C++17	100 / 100	4663 ms	47500 KiB

chorus

#include<bits/stdc++.h>
#define ll long long
#define F first 
#define S second 
using namespace std;
const ll maxn=1e18;
ll n,k,bto[1000010],bhh[1000010],hhsum[1000010];
pair<ll,ll> dp[1000010];
ll cost(ll i,ll j){
    if(i>=j)return maxn;
    ll l=max(i,bto[i]),r=j;
    return hhsum[r]-hhsum[l]-i*(r-l);
}
struct seg{
    ll pos,l,r;
    seg(ll _pos,ll _l,ll _r){
        pos=_pos,l=_l,r=_r;
    }
};
bool check(ll d){
    for(int i=1;i<=n;i++)dp[i]={maxn,0};
    deque<seg> sg;
    sg.push_back({0,1,n});
    for(int i=1;i<=n;i++){
        while(sg.front().r<i)sg.pop_front();
        ll pos=sg.front().pos;
        dp[i]={dp[pos].F+cost(pos,i)+d,dp[pos].S+1};
        while(!sg.empty()&&dp[i].F+cost(i,sg.back().l)<dp[sg.back().pos].F+cost(sg.back().pos,sg.back().l)){
            sg.pop_back();
        }
        if(sg.empty()){
            sg.push_back({i,i+1,n});
        }else{
            auto[pos,l,r]=sg.back();
            sg.pop_back();
            ll L=l,R=r;
            while(L!=R){
                int mid=(L+R+1)>>1;
                if(dp[i].F+cost(i,mid)<dp[pos].F+cost(pos,mid)){
                    R=mid-1;
                }else{
                    L=mid;
                }
            }
            sg.push_back({pos,l,L});
            if(L!=n)sg.push_back({i,L+1,n});
        }
    }
    // for(int i=1;i<=n;i++){
    //     cout<<dp[i].F-d*(dp[i].S)<<" ";
    // }
    // cout<<"\n";
    return dp[n].S>k;
}
int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    int nowa=0,nowb=0;
    cin>>n>>k;
    for(int i=0;i<2*n;i++){
        char c;
        cin>>c;
        if(c=='A'){
            nowa++;
            bhh[nowa]=nowb;
        }else{
            nowb++;
            bto[nowb]=nowa;
        }
    }
    for(int i=1;i<=n;i++){
        hhsum[i]=hhsum[i-1]+bhh[i];
    }
    ll l=0,r=maxn;
    while(l!=r){
        ll m=(l+r)>>1;
        if(check(m)){
            l=m+1;
        }else{
            r=m;
        }
    }
    check(l);
    cout<<dp[n].F-l*k<<"\n";
    return 0;
}

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