Submission #251184

#	Time	Username	Problem	Language	Result	Execution time	Memory
251184		imeimi2000	Building 4 (JOI20_building4)	C++17	100 / 100	332 ms	45548 KiB

building4

#include <bits/stdc++.h>

using namespace std;
typedef pair<int, int> pii;

const pii inf = pii(1e8, -1e8);

pii operator+(pii a, pii b) {
    return pii(min(a.first, b.first), max(a.second, b.second));
}

pii operator+(pii a, int b) {
    return pii(a.first + b, a.second + b);
}

bool operator>(pii a, int b) {
    return a.first <= b && b <= a.second;
}

int n;
int A[1000001][2];
pii dp[1000001][2];

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    cin >> n; n <<= 1;
    for (int j = 0; j < 2; ++j) for (int i = 1; i <= n; ++i)
        cin >> A[i][j];
    dp[1][0] = pii(-1, -1);
    dp[1][1] = pii(1, 1);
    for (int i = 2; i <= n; ++i) {
        for (int j = 0; j < 2; ++j) {
            dp[i][j] = inf;
            for (int k = 0; k < 2; ++k) {
                if (A[i - 1][k] <= A[i][j])
                    dp[i][j] = dp[i][j] + (dp[i - 1][k] + (j + j - 1));
            }
        }
    }
    int j;
    for (j = 0; j < 2; ++j) if (dp[n][j] > 0) break;
    if (j == 2) return printf("-1\n"), 0;
    string ans;
    for (int i = n, sum = 0; ; --i) {
        ans.push_back('A' + j);
        if (i == 1) break;
        sum -= j + j - 1;
        for (int k = 0; k < 2; ++k) {
            if (A[i - 1][k] <= A[i][j] && dp[i - 1][k] > sum) {
                j = k;
                break;
            }
        }
    }
    reverse(ans.begin(), ans.end());
    printf("%s\n", ans.c_str());
    return 0;
}

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