Submission #1278364

#	Time	Username	Problem	Language	Result	Execution time	Memory
1278364		sasde	Building 4 (JOI20_building4)	C++20	100 / 100	181 ms	28972 KiB

building4

#include<bits/stdc++.h>
using namespace std;
#define all(x) x.begin(),x.end()
#define emb emplace_back
#define ii pair<int,int>
#define fi first
#define se second
const int N=1e6+5,lg=30,mod=1e9+7,inf=1e9;
int node,a[2][N];
ii dp[N][2];
bool M2;
main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    #define task "aws"
    if(fopen(task".inp","r")){
      freopen(task".inp","r",stdin);
      freopen(task".out","w",stdout);
    }
    cin >> node ;
    for(int j=0;j<=1;++j)
    for(int i=1;i<=node*2;++i)cin >> a[j][i];
    for(int i=1;i<=node*2;++i){
        for(int j=0;j<=1;++j){
            dp[i][j]={inf,-inf};
            for(int k=0;k<=1;++k){
                if(a[j][i]<a[k][i-1])continue;
                dp[i][j].fi=min(dp[i][j].fi,dp[i-1][k].fi+(1-j));
                dp[i][j].se=max(dp[i][j].se,dp[i-1][k].se+(1-j));
            }
        }
    }
    int ok=-1;
    vector<int>res;
    // for(int i=1;i<=node*2;++i)cerr <<dp[i][0].fi<<" "<<dp[i][0].se<<" "<<dp[i][1].fi<<" "<<dp[i][1].se<<'\n';
    for(int i=0;i<=1;++i){
        if(dp[node*2][i].fi<=node&&node<=dp[node*2][i].se){
            ok=i;
        }
    }
    // cout <<ok<<" "<<node<<'\n';
    if(ok==-1){
        cout <<-1;return 0;
    }
    int cnt=node;
    for(int i=node*2;i>=1;--i){
        res.emb(ok);
        cnt-=(1-ok);
        int val=a[ok][i];
        if(val>=a[0][i-1]&&dp[i-1][0].fi<=cnt&&cnt<=dp[i-1][0].se)ok=0;
        else ok=1;
    }
    reverse(all(res));
    for(auto x:res)cout <<(!x?'A':'B');
}

Compilation message (stderr)

building4.cpp:12:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   12 | main()
      | ^~~~
building4.cpp: In function 'int main()':
building4.cpp:19:14: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   19 |       freopen(task".inp","r",stdin);
      |       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
building4.cpp:20:14: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   20 |       freopen(task".out","w",stdout);
      |       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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