Submission #1133456

#	Time	Username	Problem	Language	Result	Execution time	Memory
1133456		Zbyszek99	Building 4 (JOI20_building4)	C++20	100 / 100	154 ms	49508 KiB

building4

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;

ll A[1000001];
ll B[1000001];
pll DP[1000001][2];

int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    //random_start();
    int n;
    cin >> n;
    rep2(i,1,n*2) cin >> A[i];
    rep2(i,1,n*2) cin >> B[i];
    rep2(i,1,n*2)
    {
        //A
        DP[i][0] = {1e9,-1e9};
        DP[i][1] = {1e9,-1e9};
        if(A[i-1] <= A[i])
        {
            DP[i][0].ff = min(DP[i][0].ff,DP[i-1][0].ff+1);
            DP[i][0].ss = max(DP[i][0].ss,DP[i-1][0].ss+1);
        }
        if(B[i-1] <= A[i])
        {
            DP[i][0].ff = min(DP[i][0].ff,DP[i-1][1].ff+1);
            DP[i][0].ss = max(DP[i][0].ss,DP[i-1][1].ss+1);
        }
        if(A[i-1] <= B[i])
        {
            DP[i][1].ff = min(DP[i][1].ff,DP[i-1][0].ff);
            DP[i][1].ss = max(DP[i][1].ss,DP[i-1][0].ss);
        }
        if(B[i-1] <= B[i])
        {
            DP[i][1].ff = min(DP[i][1].ff,DP[i-1][1].ff);
            DP[i][1].ss = max(DP[i][1].ss,DP[i-1][1].ss);
        }
        //cout << DP[i][0].ff << " " << DP[i][0].ss << " " << DP[i][1].ff << " " << DP[i][1].ss << " dp\n";
    }
    ll must_A = n;
    string ans;
    int cur_v = -1;
    if(DP[n*2][0].ff <= n && DP[n*2][0].ss >= n)
    {
        cur_v = 0;
    }
    if(DP[n*2][1].ff <= n && DP[n*2][1].ss >= n)
    {
        cur_v = 1;
    }
    if(cur_v == -1)
    {
        cout << "-1\n";
        return 0;
    }
    for(int i = n*2; i >= 1; i--)
    {
        if(cur_v == 0)
        {
            must_A--;
            ans += 'A';
            if(A[i-1] <= A[i] && (DP[i-1][0].ff <= must_A && DP[i-1][0].ss >= must_A))
            {
                cur_v = 0;
            }   
            else if(B[i-1] <= A[i] && (DP[i-1][1].ff <= must_A && DP[i-1][1].ss >= must_A))
            {
                cur_v = 1;
            }   
        }
        else
        {
            ans += 'B'; 
            if(A[i-1] <= B[i] && (DP[i-1][0].ff <= must_A && DP[i-1][0].ss >= must_A))
            {
                cur_v = 0;
            }   
            else if(B[i-1] <= B[i] && (DP[i-1][1].ff <= must_A && DP[i-1][1].ss >= must_A))
            {
                
                cur_v = 1;
            }  
        }
    }
    reverse(all(ans));
    cout << ans << "\n";
}

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