Codeforces_462_B

http://codeforces.com/problemset/problem/462/B

简单的贪心，排序即可看出来。

#include<cstdio>
#include<iostream>
#include<algorithm>
using namespace std;

int main()
{
    long long a[] = {},n,k;
    long long sum = ;
    char temp;
    scanf("%lld%lld",&n,&k);
    getchar();
    for(int i = ;i < n;i++)
    {
        temp = getchar();
        a[temp-'A']++;
    }
    sort(a,a+);
    for(int i = ;i >= ;i--)
    {
        if(k <= a[i])
        {
            sum += k*k;
            break;
        }
        else
        {
            sum += a[i]*a[i];
            k -= a[i];
        }
    }
    printf("%lld\n",sum);
    return ;

}