HDU 5672 String（尺取法） - dblank

# HDU 5672 String（尺取法）

Problem Description
There is a string S.S only contain lower case English character.(10length(S)1,000,000)
How many substrings there are that contain at least k(1k26) distinct characters?

Input

There are multiple test cases. The first line of input contains an integer T(1T10) indicating the number of test cases. For each test case:

The first line contains string S.
The second line contains a integer k(1k26).

Output
For each test case, output the number of substrings that contain at least k dictinct characters.

Sample Input
2 abcabcabca 4 abcabcabcabc 3

Sample Output
0 55

Source

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<queue>
#include<map>
#include<vector>
#include<cstring>
#include<cmath>
using namespace std;
typedef long long ll;
const int INF = 0x3f3f3f3f;
const double  pi = acos(-1.0);
const int N = 1e6 + 10;
char s[N];
int main()
{
int t, k, vis[40];
cin>>t;
while(t--)
{
scanf("%s", s);
scanf("%d", &k);
memset(vis, 0, sizeof(vis));
int l = 0, r = 0, len = strlen(s), temp, num = 0;
ll ans = 0;
while(l<len)
{
while(r < len && num < k)
{
temp = s[r] - 'a';
if(!vis[temp])
num++;
vis[temp]++;
r++;
}
if(num<k)
break;
ans += len - r + 1;
temp = s[l] - 'a';
vis[temp]--;
if(vis[temp]==0)
num--;
l++;
}
cout<<ans<<endl;
}
return 0;
}