aoj2382:King_Slime.cpp

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

#define int long long
typedef vector<int>vint;
typedef pair<int,int>pint;
typedef vector<pint>vpint;
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define all(v) (v).begin(),(v).end()
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
#define pb push_back
#define fi first
#define se second
template<typename A,typename B>inline void chmin(A &a,B b){if(a>b)a=b;}
template<typename A,typename B>inline void chmax(A &a,B b){if(a<b)a=b;}

struct UF{
    vector<int>par,sz;
    vector<int>f;
    void init(int n){
        par.resize(n);
        sz.resize(n);
        f.resize(n);
        for(int i=0;i<n;i++){
            par[i]=i;
            sz[i]=1;
            f[i]=0;
        }
    }
    int find(int x){
        return x==par[x]?x:par[x]=find(par[x]);
    }
    void unite(int x,int y){
        x=find(x);y=find(y);
        if(x==y)return;
        sz[x]+=sz[y];
        f[x]|=f[y];
        par[y]=x;
    }
    bool same(int x,int y){
        return find(x)==find(y);
    }
    int size(int x){
        return sz[find(x)];
    }
};

int N,H,W;
int x[44444],y[44444];
int px[111111],py[111111];

int solve(int T){
    UF uf;uf.init(N);
    memset(px,-1,sizeof(px));
    memset(py,-1,sizeof(py));
    rep(i,N){
        if(px[x[i]]>=0)uf.unite(px[x[i]],i);
        if(py[y[i]]>=0)uf.unite(py[y[i]],i);
        if(y[i]==T)uf.f[uf.find(i)]=1;
        px[x[i]]=i;py[y[i]]=i;
    }

    int cnt1=0,cnt2=0;
    rep(i,N)if(uf.find(i)==i){
        cnt1++;
        if(uf.f[i])cnt2++;
    }

    if(cnt1==1)return N-1;
    return N-cnt1+cnt1-cnt2+cnt1-1;
}

signed main(){
    scanf("%lld%lld%lld",&N,&W,&H);
    rep(i,N)scanf("%lld%lld",&x[i],&y[i]);

    int ans=1001001001;
    rep(i,2){
        chmin(ans,solve(1));
        chmin(ans,solve(H));
        swap(H,W);
        rep(j,N)swap(x[j],y[j]);
    }
    cout<<ans<<endl;
    return 0;
}