Submission #1127688

#	Time	Username	Problem	Language	Result	Execution time	Memory
1127688		khanhphucscratch	Building 4 (JOI20_building4)	C++20	0 / 100	1 ms	328 KiB

building4

#include<bits/stdc++.h>
using namespace std;
pair<int, int> dp[1000005][2];
int a[1000005], b[1000005];
pair<int, int> add1(pair<int, int> x)
{
    x.first++; x.second++; return x;
}
pair<int, int> unite(pair<int, int> x, pair<int, int> y)
{
    //It could be unite, trust me bro
    if(x == make_pair(-1, -1)) return y;
    return make_pair(min(x.first, y.first), max(x.second, y.second));
}
bool contain(pair<int, int> y, int x)
{
    return (y.first <= x && x <= y.second);
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n; cin>>n;
    n *= 2;
    for(int i = 1; i <= n; i++) cin>>a[i];
    for(int i = 1; i <= n; i++) cin>>b[i];
    for(int i = 1; i <= n; i++) dp[i][0] = dp[i][1] = {-1, -1};
    dp[1][1] = {1, 1}, dp[1][0] = {0, 0};
    for(int i = 1; i < n; i++){
        if(a[i] < a[i+1]) dp[i+1][1] = unite(dp[i+1][1], add1(dp[i][1]));
        if(a[i] < b[i+1]) dp[i+1][0] = unite(dp[i+1][0], dp[i][1]);
        if(b[i] < a[i+1]) dp[i+1][1] = unite(dp[i+1][1], add1(dp[i][0]));
        if(b[i] < b[i+1]) dp[i+1][0] = unite(dp[i+1][0], dp[i][0]);
    }
    int num = n/2;
    if(contain(dp[n][0], num) == 0 && contain(dp[n][1], num) == 0){
        cout<<-1;
        return 0;
    }
    string ans;
    int last = 2e9;
    for(int i = n; i >= 1; i--){
        if(contain(dp[i][0], num) == 1 && last > b[i]){
            ans += "B"; last = b[i];
        }
        else{
            ans += "A"; num--; last = a[i];
        }
    }
    reverse(ans.begin(), ans.end());
    cout<<ans;
}

• Subtask 1: 0 / 11
• Subtask 2: 0 / 89