Submission #1126643

#	Time	Username	Problem	Language	Result	Execution time	Memory
1126643		VinhLuu	Building 4 (JOI20_building4)	C++20	100 / 100	249 ms	25992 KiB

building4

#include <bits/stdc++.h>
using namespace std;
  
#define ll long long
#define all(aaa) aaa.begin(), aaa.end()

const int N = 1e6 + 5;
pair<int, int> dp[N][2];
int a[N][2];
int n;

pair<int, int> mrg(pair<int, int> a, pair<int, int> b) {
	if (a.first > a.second)
		return b;
	if (b.first > b.second)
		return a;
	return {min(a.first, b.first), max(a.second, b.second)};
}
  
signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    cin >> n;

    for (int j = 0; j < 2; j++) {
    	for (int i = 0; i < n + n; i++) {
	    	cin >> a[i][j];
	    }
    }

    for (int i = 0; i <= n + n; i++) {
    	for (int j = 0; j < 2; j++) {
    		dp[i][j] = {1, 0};
    	}
    }

	dp[1][0] = {0, 0};
    dp[1][1] = {1, 1};

    for (int i = 1; i < n + n; i++) {
    	for (int j = 0; j < 2; j++) {
    		for (int k = 0; k < 2; k++) {
    			if (a[i - 1][j] <= a[i][k]) {
    				dp[i + 1][k] = mrg(dp[i + 1][k], dp[i][j]);
    			}
    		}
    	}
        dp[i + 1][1].first++;
        dp[i + 1][1].second++;
    }

    int x = n + n, y = -1, z = n;

    for (int i = 0; i < 2; i++) {
        if (dp[n + n][i].first <= n && n <= dp[n + n][i].second) {
            y = i;
            break;
        }
    }

    if (y == -1) {
        cout << "-1";
    }
    else {
        string ans;
        while (true) {
            ans.push_back({y ? 'B' : 'A'});
            if (x == 1)
                break;
            z -= y;
            x--;
            for (int i = 0; i < 2; i++) {
                if (a[x - 1][i] <= a[x][y] &&
                    dp[x][i].first <= z && z <= dp[x][i].second) {
                    y = i;
                    break;
                }
            }
        }
        reverse(all(ans));
        cout << ans << "\n";
    }

}

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