Submission #837227

#	Time	Username	Problem	Language	Result	Execution time	Memory
837227		1075508020060209tc	Love Polygon (BOI18_polygon)	C++14	75 / 100	379 ms	33440 KiB

polygon

#include <bits/stdc++.h>
using namespace std;
#define int long long

int n;
vector<int>e[200005];
vector<int>ee[200005];
int dgr[200005];
int alrd[200005];
int lve[200005];
int hs[200005];
void init(){
cin>>n;
int __id=0;
map<string,int>mp;
for(int i=1;i<=n;i++){
    string s;
    string t;
    cin>>s>>t;
    if(mp[s]==0){
        mp[s]=++__id;
    }
    if(mp[t]==0){
        mp[t]=++__id;
    }
    lve[mp[s]]=mp[t];
    e[mp[s]].push_back(mp[t]);
//    ee[mp[s]].push_back(mp[t]);
//    ee[mp[t]].push_back(mp[s]);
    dgr[mp[t]]++;
}
for(int i=1;i<=n;i++){
    if(lve[i]!=i&&lve[lve[i]]==i){
        alrd[i]=1;
        hs[i]=1;
        dgr[i]=0;
    }
}
for(int i=1;i<=n;i++){
    if(lve[i]){continue;}
    if(alrd[e[i][0]]){
        e[i][0]=i;
        dgr[i]++;
    }
}
if(n%2==1){
    cout<<"-1";exit(0);
}
}
int vis[200005];
int dp[200005];
int ans;
void dfs(int nw,int pa){
vis[nw]=1;
for(int i=0;i<ee[nw].size();i++){
    int v=ee[nw][i];
    if(v==pa){continue;}
    dfs(v,nw);
    dp[nw]+=dp[v];
    if(hs[v]==0&&hs[nw]==0){
        hs[v]=1;hs[nw]=1;
        dp[nw]++;
        ans++;
    }
}
}

int uf[200005];
int sz[200005];
int fin(int x){
if(uf[x]==x){return x;}
uf[x]=fin(uf[x]);
return uf[x];
}
void mrg(int a,int b){
int pa=fin(a);int pb=fin(b);
if(pa==pb){return;}
uf[pa]=pb;
sz[pb]+=sz[pa];
}

signed main() {
init();
ans=0;
queue<int>q;
for(int i=1;i<=n;i++){
    if(dgr[i]==0){
        q.push(i);
    }
}
while(q.size()){
    int nw=q.front();
    q.pop();
    for(int i=0;i<e[nw].size();i++){
        int v=e[nw][i];
        dgr[v]--;
        if(dgr[v]==0){
            q.push(v);
        }
        ee[v].push_back(nw);
    }
}
for(int i=1;i<=n;i++){
    if(alrd[i]){continue;}
    if(dgr[i]==1){
        dfs(i,0);
    }
}
for(int i=1;i<=n;i++){
    uf[i]=i;
    sz[i]=1;
}

for(int i=1;i<=n;i++){
    if(hs[i]){continue;}
    if(hs[lve[i]]){continue;}
    mrg(i,lve[i]);
}
for(int i=1;i<=n;i++){
    if(hs[i]){continue;}
    if(fin(i)==i){
        ans+=(sz[fin(i)]+1)/2;
    }
}
cout<<ans<<endl;
}

Compilation message (stderr)

polygon.cpp: In function 'void dfs(long long int, long long int)':
polygon.cpp:55:14: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 | for(int i=0;i<ee[nw].size();i++){
      |             ~^~~~~~~~~~~~~~
polygon.cpp: In function 'int main()':
polygon.cpp:94:18: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   94 |     for(int i=0;i<e[nw].size();i++){
      |                 ~^~~~~~~~~~~~~

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