poj 2513 Colored Sticks 欧拉路

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
using namespace std;
const int maxn=250005;
struct pi{
char c[10];
}pp[maxn*2];
struct ppi{
char c[10],d[10];
}pp1[maxn];
int cmp(pi a,pi b){
return strcmp(a.c,b.c)<0;
}
int in[2*maxn];
int get(char *c,int n){
int le=0;
int ri=n-1;
int mid;
while(le<=ri){
mid=(le+ri)/2;
if(strcmp(pp[mid].c,c)>=0) ri=mid-1;
else le=mid+1;
}
return le;
}
int pa[maxn*2];
int find(int p){
if(pa[p]==p) return p;
return pa[p]=find(pa[p]);
}
void merg(int a,int b){
int x,y;
x=find(a);
y=find(b);
pa[x]=y;
}
int main()
{
int i,n;
n=0;
while(scanf("%s%s",pp1
.c,pp1
.d)!=EOF){
strcpy(pp[2*n].c,pp1
.c);
strcpy(pp[2*n+1].c, pp1
.d);
n++;
}
/*  cin>>n;
for(i=0;i<n;i++){
scanf("%s%s",pp1
.c,pp1
.d);
strcpy(pp[2*n].c,pp1
.c);
strcpy(pp[2*n+1].c, pp1
.d);
}*/
sort(pp,pp+2*n,cmp);
for(i=0;i<2*n;i++) pa[i]=i;
int w=0;
for(i=0;i<n;i++){
int a,b;
a=get(pp1[i].c,2*n);
b=get(pp1[i].d,2*n);
in[a]++;
in[b]++;
merg(a,b);
w=a;
}
int x=0;
for(i=0;i<2*n;i++){
if(in[i]%2==1) x++;
}
int f=0;
for(i=0;i<2*n;i++){
if(in[i]!=0){
if(find(i)!=find(w)){
f=1;
break;
}
}
}
if(x>2||f) printf("Impossible\n");
else printf("Possible\n");
}