Submission #824984

#	Time	Username	Problem	Language	Result	Execution time	Memory
824984		xink	Building 4 (JOI20_building4)	C++14	100 / 100	645 ms	25900 KiB

building4

#include <iostream>
#include <vector>
#include <utility>
#include <sstream>
#include <climits>
#include <cstring>
#include <algorithm>
#define ll long long
#define ld long double
using namespace std;
const ll mod = 1e9 + 7;
const int maxn = 5e5 + 5, maxn1 = 2e3 + 5;
typedef vector<int> vi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
bool can_construct[maxn1][maxn1][2];
int arr[2 * maxn][2], dp_min[2 * maxn][2], dp_max[2 * maxn][2];

void solve()
{
    int n;
    cin >> n;
    for (int i = 0; i < 2 * n; i++)
    {
        cin >> arr[i][0];
    }
    for (int i = 0; i < 2 * n; i++)
    {
        cin >> arr[i][1];
    }
    dp_min[0][0] = 0, dp_max[0][0] = 0;
    dp_min[0][1] = 1, dp_max[0][1] = 1;
    for (int i = 1; i < 2 * n; i++)
    {
        for (int curr = 0; curr < 2; curr++)
        {
            dp_min[i][curr] = i + 1;
            for (int prev = 0; prev < 2; prev++)
            {
                if (arr[i][curr] >= arr[i - 1][prev])
                {
                    dp_min[i][curr] = min(dp_min[i][curr], dp_min[i - 1][prev] + curr);
                    dp_max[i][curr] = max(dp_max[i][curr], dp_max[i - 1][prev] + curr);
                }
            }
        }
    }
    int curr_arr = -1, n_arr1 = n;
    for (int i = 0; i < 2; i++)
    {
        if (dp_min[2 * n - 1][i] <= n && n <= dp_max[2 * n - 1][i])
        {
            curr_arr = i;
            break;
        }
    }
    if (curr_arr == -1)
    {
        cout << -1;
        return;
    }
    string ans;
    for (int i = 2 * n - 1; i >= 0; i--)
    {
        ans += (curr_arr ? 'B' : 'A');
        for (int nxt = 0; nxt < 2; nxt++)
        {
            if (i > 0 && arr[i][curr_arr] >= arr[i - 1][nxt] && dp_min[i - 1][nxt] <= n_arr1 - curr_arr && n_arr1 - curr_arr <= dp_max[i - 1][nxt])
            {
                n_arr1 -= curr_arr;
                curr_arr = nxt;
                break;
            }
        }
    }
    reverse(ans.begin(), ans.end());
    cout << ans;
}

int main()
{
    // freopen("input_text", "r", stdin);
    // freopen("output_text", "w", stdout);
    // ios_base::sync_with_stdio(NULL); cin.tie(0); cout.tie(0);
    int t = 1;
    // cin >> t;
    while (t-- > 0)
        solve();
}

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