2016HUAS暑假集训训练2 A - Is It A Tree?

#include<iostream>
#include <cstring>
using namespace std;
int main()
{

    int n = 0, x, y, fff, i, j,sss[15], t = 0, k = 0, s ,ss, f, ff = 0, a[10005], b[10005], r[10005];

    while (cin >> x >> y)
    {
        if (x <0 || y <0) break;
        ff ++;
        if (x == 0 && y == 0 && t == 0 && k == 0)//空数也是数   易忽略
        {
            cout << "Case " << ++n << " is a tree." << endl;
            t = 0; k = 0; ff = 0;

            continue;
        }
        a[t++] = y;  //保存入度的点
        b[k++] = x; b[k++] = y; // 保存所有的点
        if (x == 0 && y == 0 && (t != 0 && k != 0))
        {
             ss = 0;
             memset(sss,0,sizeof(sss));
            for (i = 0 ; i < k - 1; i ++)
                 sss[b[i]] ++;
                 for(i = 0; i <= 15; i ++)//找到顶点数
                 if(sss[i] > 0) ss ++;
            f = 1; s = 0;
            for (i = 0; i < t - 1; i ++) //判断是否入度是否有大于2的和找到入度为一的个数
            {
                for (j = i + 1; j < t; j ++)
                {
                    if (a[i] == a[j])
                    {
                        f = 0; break;
                    }
                }
                s++;
            }
            
            if (f == 1 && ss - s == 2 && ss - ff == 1&&ff - s == 1)//根据定义判断是否是树
                cout << "Case " << ++n << " is a tree." << endl;
            else
                cout << "Case " << ++n << " is not a tree." << endl;

                 t = 0; k = 0; ff = 0;
        }

    }
    return 0;
}