HDU 5056 Boring count（数学）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=5056

Problem Description You are given a string S consisting of lowercase letters, and your task is counting the number of substring that the number of each lowercase letter in the substring is no more than K.   Input In the first line there is an integer T , indicates the number of test cases.
For each case, the first line contains a string which only consist of lowercase letters. The second line contains an integer K.

[Technical Specification]
1<=T<= 100
1 <= the length of S <= 100000
1 <= K <= 100000   Output For each case, output a line contains the answer.   Sample Input

3
abc
1
abcabc
1
abcabc
2

  Sample Output

6
15
21

  Source BestCoder Round #11 (Div. 2)

官方题解:

代码例如以下：

#include <cstdio>
#include <cstring>
const int maxn = 100017;
int main()
{
int t;
char str[maxn];
int st[27];
int k;
scanf("%d",&t);
while(t--)
{
memset(st,0,sizeof(st));
scanf("%s",str);
scanf("%d",&k);
__int64 ans = 0;
int len = strlen(str);
int startpos = 0;
for(int i = 0; i < len; i++)
{
int tt = str[i] -'a';
st[tt]++;
if(st[tt] > k)
{
while(str[startpos]!=str[i])
{
st[str[startpos]-'a']--;
startpos++;
}
st[str[startpos]-'a']--;
startpos++;
}
ans+=i-startpos+1;
}
printf("%I64d\n",ans);
}
return 0;
}