uva 10596 Morning Walk

题目：https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=17&page=show_problem&problem=1537

给出的点不一定有边通过,而且m==0输出Not Possible;

两大坑

#include<cstdio>
#include<string>
#include<cstring>
#include<iostream>
#include<cmath>
#include<algorithm>
#include<climits>
#include<queue>
#include<vector>
#include<map>
#include<sstream>
#include<set>
#include<stack>
#include<utility>
#pragma comment(linker, "/STACK:102400000,102400000")
#define PI 3.1415926535897932384626
#define eps 1e-10
#define sqr(x) ((x)*(x))
#define FOR0(i,n)  for(int i=0 ;i<(n) ;i++)
#define FOR1(i,n)  for(int i=1 ;i<=(n) ;i++)
#define FORD(i,n)  for(int i=(n) ;i>=0 ;i--)
#define  lson   num<<1,le,mid
#define rson    num<<1|1,mid+1,ri
#define MID   int mid=(le+ri)>>1
#define zero(x)((x>0? x:-x)<1e-15)

using namespace std;
const int INF =0x3f3f3f3f;
const int maxn=  200+10  ;
const int maxm=  10000 +10;
//const int INF=    ;
typedef long long ll;
const ll inf =1000000000000000;//1e15;
//ifstream fin("input.txt");
//ofstream fout("output.txt");
//fin.close();
//fout.close();
//freopen("a.in","r",stdin);
//freopen("a.out","w",stdout);
int in[maxn];
int pre[maxn];
int n,m;
int find(int x)
{
    return x==pre[x]?x:pre[x]=find(pre[x]);
}

void merge(int u ,int v)
{
    int x=find(u);
    int y=find(v);
    if(x!=y)
    pre[x]=y;
}
void init()
{
    for(int i=0;i<n;i++)
    {
            pre[i]=i;
            in[i]=0;
    }
}

int main()
{
    int x,y;
    while(~scanf("%d%d",&n,&m))
    {
        init();
        FOR1(i,m)
        {
            scanf("%d%d",&x,&y);
            merge(x,y);
            in[x]++;in[y]++;
        }
        int prin=find(0);
        bool ok=1;
        for(int i=0;i<n;i++)
        {
            if(  in[i]&& prin!=find(i)|| in[i]%2 )
                ok=0;
        }
        if(!ok ||!m) puts("Not Possible");
            else puts("Possible");

    }

    return 0;
}