Submission #377009

#	Time	Username	Problem	Language	Result	Execution time	Memory
377009		lertwqen243	Love Polygon (BOI18_polygon)	C++14	100 / 100	196 ms	30776 KiB

polygon

#include <bits/stdc++.h>
using namespace std;
         
const int N = 1e5 + 5;
         
int n,love[N];
int ind;
unordered_map<string,int>id;
vector <int> g[N],adj[N];
bool mrk[N];
vector<int>ord;
deque<int>dag;

void dfs(int v){
    mrk[v]=1;
    for (int i=0;i<(int)g[v].size();i++){
        int u=g[v][i];
        if (!mrk[u]){
            adj[v].push_back(u); 
            dfs(u);
        }
    }
    ord.push_back(v);
    return;
}
int used[N];
int max_maching;
bool mark[N];
void maching_dfs(int v, int par){
    for(int i=0;i<(int)adj[v].size();i++){
        int u=adj[v][i];
        maching_dfs(u,v);
    }
    if(!used[v] && !used[par] && par!=0){
        max_maching++;
        used[v]=used[par]=1;
    }
}
inline int solve1(int root){
    max_maching = 0;
    for(int i=0;i<(int)ord.size();i++){
        int v=ord[i];
        used[v]=0;
    }
    maching_dfs(root,0);
    return max_maching;
}
inline int solve2(int root){
    if(love[root]==root) return 0;
    for(int i=0;i<(int)ord.size();i++){
        int v=ord[i];
        used[v]=0;
    }
    used[root]=used[love[root]]=1;
    max_maching=0;
    maching_dfs(root,0);
    return max_maching+1+(int)(love[love[root]]==root);
}
void DFS(int v){
    mrk[v]=1;
    for(int i=0;i<(int)g[v].size();i++){
        int u=g[v][i];
        if(mrk[u]) continue;
        DFS(u);
    }
    dag.push_back(v);
    return;
}
void fsd(int v){
    mrk[v]=1;
    for(int i=0;i<(int)g[v].size();i++){
        int u=g[v][i];
        if(!mrk[u]){
            adj[v].push_back(u);
            fsd(u);
        }
    }
    ord.push_back(v);
    return;
}
int main() {
    ios_base::sync_with_stdio(0),cin.tie(0);cout.tie(0);
    cin>>n;
    if(n%2){
        cout<<"-1\n";
        return 0;
    }
    for(int i=1;i<=n;i++){
        string a,b;
        cin>>a>>b;
        if(id.count(a)==0){
            id[a]=++ind;
        }
        if(id.count(b)==0){
            id[b]=++ind;
        }
        int u=id[a];
        int v=id[b];
        love[u]=v;
        g[v].push_back(u);
    }
    for(int i=1;i<=n;i++){
        if(!mrk[i]){
            DFS(i);
        }
    }
    for(int i=1;i<=n;i++){mrk[i]=0;}
    int ans=n;
    while(dag.size()){
        int v=dag.back();dag.pop_back();
        if(mrk[v])continue;
        ord.clear();fsd(v);
        ans-=max(solve1(v),solve2(v));
    }
    cout<<ans<<'\n';
    return 0;
}

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