Submission #969707

#	Time	Username	Problem	Language	Result	Execution time	Memory
969707		Darren0724	Love Polygon (BOI18_polygon)	C++17	0 / 100	209 ms	21840 KiB

polygon

#include<bits/stdc++.h>
using namespace std;
const int N=100005;
map<string,int> m;
vector<int> vis(N),deg(N);
vector<int> v(N,-1),in(N);
inline int id(string s){
    if(m.count(s)){
        return m[s];
    }
    int p=m.size();
    m[s]=p;
    return p;
}
int32_t main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n;cin>>n;
    if(n&1){
        cout<<-1<<endl;
        return 0;
    }
    for(int i=0;i<n;i++){
        string a,b;cin>>a>>b;
        v[id(a)]=id(b);
        in[id(b)]++;
        if(v[id(b)]==id(a)&&a!=b){
            vis[id(a)]=vis[id(b)]=1; 
        }
    }
    int ans=0;
    queue<int> q;
    for(int i=0;i<n;i++){
        if(in[i]==0){
            q.push(i);
        }
    }
    while(q.size()){
        int p=q.front();
        q.pop();
        //cout<<p<<endl;
        deg[v[p]]--;
        if(deg[v[p]]==0){
            q.push(v[p]);
        }
        if(vis[p]||vis[v[p]]){
            continue;
        }
        ans++;
        vis[p]=vis[v[p]]=1;
    }
    for(int i=0;i<n;i++){
        if(vis[i])continue;
        int sz=0,f=i;
        while(vis[f]==0){
            sz++;
            vis[f]=1;
            f=v[f];
        }
        assert(sz==1);
        ans+=(sz+1)/2;
    }
    cout<<ans<<endl;
 
    return 0;
}

• Subtask 1: 0 / 21
• Subtask 2: 0 / 25
• Subtask 3: 0 / 29
• Subtask 4: 0 / 25