Usaco Riding the Fences

This question is very interesting ......

Good code:

/*ID: guo geerPROG: fenceLANG: C++*/#include<iostream>#include<cstring>#include<cmath>#include<fstream>using namespace std;int a[510][510],b[510],path[1029],stack[1029];int getMin(int s[]){    for(int i=1; i<=500; i++)    if(s[i] > 0) return i;    return -1;}int main(){    ifstream fin("fence.in");    ofstream fout("fence.out");        int F;    while(fin>>F)    {        memset(a, 0, sizeof(a));        memset(b, 0, sizeof(b));                int x,y,st=510;        for(int i=0; i<F; i++)        {                fin>>x>>y;                st=min(st,min(x,y));                a[x][y] ++;                a[y][x] ++;                b[x] ++;                b[y] ++;        }        for(int i=1; i<=500; i++) if(b[i]%2 == 1){st = i; break;}                int p = 0, top=-1;        stack[++ top] = st;        while(top != -1)        {              st = stack[top];              if(b[st] == 0) path[p ++] = st, top --;              while(b[st] > 0)              {                     int tt = getMin(a[st]);                                          b[st] --;                     b[tt] --;                      a[st][tt] --;                     a[tt][st] --;                                      st = tt;                     stack[++top] = st;              }        }        for(int i=F; i>=0; i--) fout<<path[i]<<endl;    }    return 0;}