Submission #942648

#	Time	Username	Problem	Language	Result	Execution time	Memory
942648		guagua0407	Building 4 (JOI20_building4)	C++17	0 / 100	1 ms	348 KiB

building4

//#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define f first
#define s second
#define all(x) x.begin(),x.end()
#define _ ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

int dx[4]={0,0,1,-1};
int dy[4]={1,-1,0,0};

void setIO(string s) {
    freopen((s + ".in").c_str(), "r", stdin);
    freopen((s + ".out").c_str(), "w", stdout);
}

const int inf=1e9;

int main() {_
    int n;
    cin>>n;
    n*=2;
    vector<vector<int>> vec(n,vector<int>(2));
    for(int i=0;i<n;i++){
        cin>>vec[i][0];
    }
    for(int i=0;i<n;i++){
        cin>>vec[i][1];
    }
    vector<int> dir(n);
    for(int i=0;i<n;i++){
        if(vec[i][0]>vec[i][1]){
            swap(vec[i][0],vec[i][1]);
            dir[i]=1;
        }
    }
    vector<int> ans(n);
    ans[0]=dir[0];
    for(int i=1;i<n;i++){
        int prv=vec[i-1][ans[i-1]^dir[i-1]];
        if(prv<=vec[i][0]) ans[i]=dir[i];
        else if(prv<=vec[i][1]) ans[i]=dir[i]^1;
        else{
            cout<<-1<<'\n';
            return 0;
        }
    }
    int cur=0;
    for(int i=0;i<n;i++){
        if(ans[i]==0) cur++;
    }
    //cout<<cur<<'\n';
    for(int r=n-1;cur!=n/2 and r>=0;r--){
        int l=r-1;
        while(l>=0 and (vec[l][0]<=vec[l+1][0] and vec[l][1]<=vec[l+1][1] and vec[l][1]>vec[l+1][0])){
            l--;
        }
        l++;
        //cout<<l<<' '<<r<<'\n';
        bool ok1=(l==0 or vec[l-1][ans[l-1]^dir[l-1]]<=vec[l][0]);
        bool ok2=(r==n-1 or vec[r][1]<=vec[r+1][ans[r+1]^dir[r+1]]);
        if(!ok1 or !ok2){
            r=l;
            continue;
        }
        for(int i=l;i<=r;i++){
            assert(ans[i]==dir[i]);
        }
        vector<pair<int,int>> dif;
        dif.push_back({0,r+1});
        for(int i=r;i>=l;i--){
            dif.push_back({dif.back().f+(dir[i]==0?-1:1),i});
        }
        /*reverse(all(dif));
        for(auto v:dif){
            cout<<v.f<<' '<<v.s<<'\n';
        }*/
        sort(all(dif));
        int pos;
        if(cur<=n/2){
            pos=upper_bound(all(dif),make_pair(n/2-cur,inf))-dif.begin()-1;
        }
        else{
            pos=lower_bound(all(dif),make_pair(n/2-cur,inf))-dif.begin();
        }
        int b=dif[pos].s;
        cur+=dif[pos].f;
        for(int i=r;i>=b;i--){
            ans[i]=dir[i]^1;
        }
        r=l;
    }
    if(cur!=n/2){
        cout<<-1<<'\n';
        return 0;
    }
    for(int i=0;i<n;i++){
        cout<<(ans[i]==0?'A':'B');
    }
    cout<<'\n';
    return 0;
}
//maybe its multiset not set
//yeeorz
//laborz

Compilation message (stderr)

building4.cpp: In function 'void setIO(std::string)':
building4.cpp:15:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 |     freopen((s + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
building4.cpp:16:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |     freopen((s + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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