Submission #623026

#	Time	Username	Problem	Language	Result	Execution time	Memory
623026		radal	Building 4 (JOI20_building4)	C++17	100 / 100	253 ms	45356 KiB

building4

#include <bits/stdc++.h>
#pragma GCC target("sse,sse2,avx2")
#pragma GCC optimize("unroll-loops,O2")
#define rep(i,l,r) for (int i = l; i < r; i++)
#define repr(i,r,l) for (int i = r; i >= l; i--)
#define X first
#define Y second
#define all(x) (x).begin() , (x).end()
#define pb push_back
#define endl '\n'
#define debug(x) cerr << #x << " : " << x << endl;
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pll;
constexpr int N = 1e6+10,mod = 998244353,inf = 1e9+10,sq = 700;
inline int mkay(int a,int b){
    if (a+b >= mod) return a+b-mod;
    if (a+b < 0) return a+b+mod;
    return a+b;
}
 
inline int poww(int a,int k){
    if (k < 0) return 0;
    int z = 1;
    while (k){
        if (k&1) z = 1ll*z*a%mod;
        a = 1ll*a*a%mod;
        k /= 2;
    } 
    return z; 
}
int n,a[N],b[N];
int mx[N][2],mi[N][2];
int main(){
    ios :: sync_with_stdio(0); cin.tie(0);
    cin >> n;
    n *= 2;
    rep(i,0,n) cin >> a[i];
    rep(i,0,n) cin >> b[i];
    int cur = 0;
    rep(i,0,n){
        if (max(a[i],b[i]) < cur){
            cout << -1 << endl;
            return 0;
        }
        if (min(a[i],b[i]) >= cur){
            cur = min(a[i],b[i]);
        }
        else cur = max(a[i],b[i]);
    }
    mx[n-1][0] = mi[n-1][0] = 1;
    mx[n-1][1] = mi[n-1][1] = -1;
    repr(i,n-2,0){
        mx[i][0] = mx[i][1] = -inf;
        mi[i][0] = mi[i][1] = inf;
        if (a[i] <= a[i+1]){
            mx[i][0] = max(mx[i][0],mx[i+1][0]+1);
            mi[i][0] = min(mi[i][0],mi[i+1][0]+1);
        }
        if (a[i] <= b[i+1]){
            mx[i][0] = max(mx[i][0],mx[i+1][1]+1);
            mi[i][0] = min(mi[i][0],mi[i+1][1]+1);
        }
        if (b[i] <= a[i+1]){
            mx[i][1] = max(mx[i][1],mx[i+1][0]-1);
            mi[i][1] = min(mi[i][1],mi[i+1][0]-1);
        }
        if (b[i] <= b[i+1]){
            mx[i][1] = max(mx[i][1],mx[i+1][1]-1);
            mi[i][1] = min(mi[i][1],mi[i+1][1]-1);
        }
    }
    if ((mi[0][0] > 0 || mx[0][0] < 0) && (mi[0][1] > 0 || mx[0][1] < 0)){
        cout << -1;
        return 0;
    }
    cur = 0;
    int s = 0;
    string ans = "";
    rep(i,0,n){
        if (min(a[i],b[i]) < cur){
            cur = max(a[i],b[i]);
            if (a[i] == cur){
                s++;
                ans += 'A';
            }
            else{
                s--;
                ans += 'B';
            }
            continue;
        }
        if (i == n-1){
            if (s == -1) ans += 'A';
            else ans += 'B';
            continue;
        }
        if ((a[i+1] < a[i] || mi[i+1][0] > -s-1 || mx[i+1][0] < -s-1) && (b[i+1] < a[i] || mi[i+1][1] > -s-1 || mx[i+1][1] < -s-1)){
            ans += 'B';
            s--;
            cur = b[i];
        }
        else{
            ans += 'A';
            s++;
            cur = a[i];
        }
    }
    cout << ans;
    return 0;
}

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