poj 2513 Colored Sticks 欧拉路

水欧拉路，直接颜色离散化然后建边，或者并查集。

#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[n].c,pp1[n].d)!=EOF){
        strcpy(pp[2*n].c,pp1[n].c);
        strcpy(pp[2*n+1].c, pp1[n].d);
        n++;
    }
  /*  cin>>n;
    for(i=0;i<n;i++){
        scanf("%s%s",pp1[n].c,pp1[n].d);
        strcpy(pp[2*n].c,pp1[n].c);
        strcpy(pp[2*n+1].c, pp1[n].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");
}