Appleman has n cards. Each card has an uppercase letter written on it. Toastman must choose k cards from Appleman‘s cards. Then Appleman should give Toastman some coins depending on the chosen cards. Formally, for each Toastman‘s card i you should calculate how much Toastman‘s cards have the letter equal to letter on ith, then sum up all these quantities, such a number of coins Appleman should give to Toastman.

Given the description of Appleman‘s cards. What is the maximum number of coins Toastman can get?

The first line contains two integers n and k (1 ≤ k ≤ n ≤ 105). The next line contains n uppercase letters without spaces — the i-th letter describes the i-th card of the Appleman.

Print a single integer – the answer to the problem.

In the first test example Toastman can choose nine cards with letter D and one additional card with any letter. For each card with D he will get 9 coins and for the additional card he will get 1 coin.

解题：贪心。

 1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 #include <cmath> 5 #include <algorithm> 6 #include <climits> 7 #include <vector> 8 #include <queue> 9 #include <cstdlib>10 #include <string>11 #include <set>12 #include <stack>13 #define LL long long14 #define pii pair<int,int>15 #define INF 0x3f3f3f3f16 using namespace std;17 int letter[27];18 char str[100100];19 bool cmp(const int &x,const int &y){20     return x > y;21 }22 int main() {23     int n,k;24     LL ans;25     while(~scanf("%d %d",&n,&k)){26         memset(letter,0,sizeof(letter));27         scanf("%s",str);28         for(int i = 0; str[i]; i++) letter[str[i]-‘A‘]++;29         sort(letter,letter+26,cmp);30         for(int i = ans = 0; k && i < 26; i++){31             ans += 1LL*min(k,letter[i])*min(k,letter[i]);32             k -= min(k,letter[i]);33         }34         cout<<ans<<endl;35     }36     return 0;37 }

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