Submission #1012824

#	Time	Username	Problem	Language	Result	Execution time	Memory
1012824		denislav	Building 4 (JOI20_building4)	C++14	100 / 100	208 ms	45592 KiB

building4

# include <iostream>
# include <vector>
# include <algorithm>
# include <cassert>
using namespace std;

const int MAX=1e6+11,INF=1e9;
int a[2][MAX];
pair<int, int> dp[2][MAX];
int n;

void reset()
{
    for(int i=1;i<=n*2;i++)
    {
        for(int k=0;k<=1;k++)
        {
            dp[k][i]={INF,-INF};
        }
    }
}

vector<char> ve;
void rec(int k, int i, int v)
{
    if(k==0) ve.push_back('A');
    else ve.push_back('B');

    if(i==1) return ;

    int pr=v;
    if(k==1) pr++;
    else pr--;

    if(dp[0][i-1].first!=INF and dp[0][i-1].first<=pr and pr<=dp[0][i-1].second and a[k][i]>=a[0][i-1]) rec(0,i-1,pr);
    else rec(1,i-1,pr);
}

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

    cin>>n;
    for(int k=0;k<=1;k++)
    {
        for(int i=1;i<=n*2;i++) cin>>a[k][i];
    }

    reset();

    dp[0][1]={1,1};
    dp[1][1]={-1,-1};
    for(int i=1;i<n*2;i++)
    {
        for(int k=0;k<=1;k++)
        {
            if(dp[k][i].first==INF) continue;

            if(a[k][i]<=a[0][i+1])
            {
                int l=dp[k][i].first+1;
                int r=dp[k][i].second+1;
                dp[0][i+1].first=min(dp[0][i+1].first,l);
                dp[0][i+1].second=max(dp[0][i+1].second,r);
            }

            if(a[k][i]<=a[1][i+1])
            {
                int l=dp[k][i].first-1;
                int r=dp[k][i].second-1;
                dp[1][i+1].first=min(dp[1][i+1].first,l);
                dp[1][i+1].second=max(dp[1][i+1].second,r);
            }
        }
    }

    /*
    for(int i=1;i<=n*2;i++)
    {
        for(int k=0;k<=1;k++)
        {
            cout<<i<<" "<<k<<":"<<dp[k][i].first<<" "<<dp[k][i].second<<"\n";
        }
    }
    */


    if(!(dp[0][n*2].first<=0 and dp[0][n*2].second>=0) and !(dp[1][n*2].first<=0 and dp[1][n*2].second>=0)) {cout<<"-1"<<"\n";return 0;}

    if(dp[0][n*2].first<=0 and dp[0][n*2].second>=0) rec(0,n*2,0);
    else rec(1,n*2,0);

    reverse(ve.begin(),ve.end());
    for(char x: ve) cout<<x;
    cout<<"\n";

    return 0;
}

• Subtask 1: 11 / 11
• Subtask 2: 89 / 89