Submission #212516

#	Time	Username	Problem	Language	Result	Execution time	Memory
212516		combi1k1	Building 4 (JOI20_building4)	C++14	100 / 100	330 ms	27500 KiB

building4

#include<bits/stdc++.h>

using namespace std;

#define ll  long long
#define ld  double

#define sz(x)   (int)x.size()
#define all(x)  x.begin(),x.end()

#define pb  emplace_back
#define X   first
#define Y   second

const int   N   = 1e6 + 5;

typedef pair<int,int>   ii;

int a[N][2];
int l[N][2];
int r[N][2];

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

    int n;  cin >> n;   n += n;

    for(int i = 1 ; i <= n ; ++i)   cin >> a[i][0];
    for(int i = 1 ; i <= n ; ++i)   cin >> a[i][1];

    for(int i = 1 ; i <= n ; ++i)   {
        l[i][0] = l[i][1] = 1e9;
        r[i][0] = r[i][1] = -1e9;

        for(int x = 0 ; x < 2 ; ++x)
        for(int y = 0 ; y < 2 ; ++y)    if (a[i - 1][x] <= a[i][y]) {
            l[i][y] = min(l[i][y],l[i - 1][x] + (y == 0));
            r[i][y] = max(r[i][y],r[i - 1][x] + (y == 0));
        }
    }
    int S = 0;
    int v = n / 2;

    if (l[n][0] > v)    S = 1;
    if (r[n][0] < v)    S = 1;

    if (l[n][S] > v)    return  cout << "-1",0;
    if (r[n][S] < v)    return  cout << "-1",0;

    string res = "";

    for(int i = n ; i >= 1 ; --i)   {
        if (S == 0) res += 'A', --v;
        if (S == 1) res += 'B';

        for(int x = 0 ; x < 2 ; ++x)    if (a[i - 1][x] <= a[i][S]) {
            if (l[i - 1][x] > v)    continue;
            if (r[i - 1][x] < v)    continue;

            S = x;
            break;
        }
    }

    reverse(all(res));

    cout << res << endl;
}

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