Submission #999702

#	Time	Username	Problem	Language	Result	Execution time	Memory
999702		Unforgettablepl	Building 4 (JOI20_building4)	C++17	100 / 100	193 ms	44528 KiB

building4

#include <bits/stdc++.h>
using namespace std;

#define int long long


int32_t main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;
    vector<int> A(2*n+2);
    vector<int> B(2*n+2);
    A[2*n+1]=B[2*n+1]=1e9;
    vector<bool> chosen(2*n+1);
    vector<int> val(2*n+2);val[2*n+1]=1e9;
    for(int i=1;i<=2*n;i++)cin>>A[i];
    for(int i=1;i<=2*n;i++)cin>>B[i];
    int cntB = 0;
    for(int i=1;i<=2*n;i++){
        if(A[i]<=B[i]){
            if(A[i]>=val[i-1])val[i]=A[i];
            else if(B[i]>=val[i-1]){
                chosen[i]=true;
                val[i]=B[i];
                cntB++;
            } else {
                cout << "-1\n";
                return 0;
            }
        } else {
            if(B[i]>=val[i-1]){
                chosen[i]=true;
                val[i]=B[i];
                cntB++;
            } else if(A[i]>=val[i-1])val[i]=A[i];
            else {
                cout << "-1\n";
                return 0;
            }
        }
    }
    int cntA = 2*n-cntB;
    int end = -1;
    int cost = 0;
    if(cntA<cntB){
        int target = n-cntA;
        for(int i=2*n;i;i--){
            if(target==0)break;
            if((A[i]<B[i] and chosen[i]) or (A[i]>B[i] and !chosen[i])){end=-1;cost=0;continue;} // Already maximum
            if(max(A[i],B[i])>max(A[i+1],B[i+1])){end=-1;cost=0;continue;} // Can't be flipped
            if(max(A[i],B[i])<=val[i+1]){end=i;cost=0;}
            else if(end==-1)continue;
            if(chosen[i])cost++;
            else cost--;
            if(cost==1){
                for(int j=i;j<=end;j++){
                    chosen[j]=!chosen[j];
                    val[j]=max(A[j],B[j]);
                }
                target--;
                cost = 0;
                end = -1;
            }
        }
        if(target!=0){
            cout << "-1\n";
            return 0;
        }
    } else if(cntB<cntA){
        int target = n-cntB;
        for(int i=2*n;i;i--){
            if(target==0)break;
            if((A[i]<B[i] and chosen[i]) or (A[i]>B[i] and !chosen[i])){end=-1;cost=0;continue;} // Already maximum
            if(max(A[i],B[i])>max(A[i+1],B[i+1])){end=-1;cost=0;continue;} // Can't be flipped
            if(max(A[i],B[i])<=val[i+1]){end=i;cost=0;}
            else if(end==-1)continue;
            if(chosen[i])cost--;
            else cost++;
            if(cost==1){
                for(int j=i;j<=end;j++){
                    chosen[j]=!chosen[j];
                    val[j]=max(A[j],B[j]);
                }
                target--;
                cost = 0;
                end = -1;
            }
        }
        if(target!=0){
            cout << "-1\n";
            return 0;
        }
    }
    for(int i=1;i<=2*n;i++)cout<<(chosen[i]?'B':'A');
    cout << '\n';
}

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