題意：給定n個名字，取k個名字，若每個名字的長度與這k串名字的平均長度的差值(絕對值)都不大於2，則符合要求。判斷這n個名字分成K組是否符合要求。

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<queue>
#include<vector>
#include<cmath>
#include<set>
using namespace std;
const int maxn = 1e9;
const int maxt = 1e8;
const double eps = 1e-6;
typedef long long ll;
const ll MOD = 1e9;
char name[110];
int len[1010];
int n, k;
int main()
{
    int kase = 0;
    while(~scanf("%d%d",&n,&k))
    {
        if(!n && !k) break;
        if(kase) printf("\n");
        for(int i = 0; i < n; i++)
        {
            scanf("%s",name);
            len[i] = strlen(name);
        }
        sort(len, len + n);
        bool ok = true;
        int l = n / k;
        for(int i = 0; i < l; i++)
        {
            int sum = 0;
            for(int j = 0; j < k; j++)
            {
                sum += len[j + i * k];
            }
            double aver = (double)sum / k;
            for(int j = 0; j < k; j++)
                if(fabs(len[j + i * k] - aver) - 2.0 > eps)
                    {ok = false; break;}
        }
        if(ok) printf("Case %d: yes\n",++kase);
        else   printf("Case %d: no\n",++kase);
    }
    return 0;
}