Luogu P1333 瑞瑞的木棍 并查集&&字符串？

// luogu-judger-enable-o2
// luogu-judger-enable-o2
#include<cstdio>
#include<iostream>
#include<cstring>
//#include<unordered_map>
#include<map>
#define R register int
using namespace std;
//unordered_map<string,int>mp;
map<string,int> mp;
inline int g() {
    R ret=0,fix=1; register char ch; while(!isdigit(ch=getchar())) fix=ch==‘-‘?-1:fix;
    do ret=ret*10+(ch^48); while(isdigit(ch=getchar())); return ret*fix;
}
int n,m,cnt,num,tot;
int fa[500010],mu[250010],mv[250010],r[500010];
int getf(int x) {return x==fa[x]?x:fa[x]=getf(fa[x]);}
inline void merge(int u,int v) {
    u=getf(u),v=getf(v); if(u==v) return ; 
    fa[u]=v;
}
signed main() { register char u[11],v[11];
    while(~scanf("%s%s",u,v)) { R uu,vv;
        if(mp.find(u)==mp.end()) uu=mp[u]=++num; else uu=mp[u];
        if(mp.find(v)==mp.end()) vv=mp[v]=++num; else vv=mp[v]; mu[++cnt]=uu,mv[cnt]=vv; ++r[uu],++r[vv];
    } for(R i=1;i<=num;++i) fa[i]=i; for(R i=1;i<=cnt;++i) merge(mu[i],mv[i]);
    for(R i=1;i<=num;++i) if(getf(i)==i) ++tot;
    if(tot>1) {printf("Impossible\n"); return 0;} cnt=0;
    for(R i=1;i<=num;++i) cnt+=(r[i]&1);
    (cnt==0||cnt==2)?printf("Possible\n"):printf("Impossible\n");
}