Sanket and strings

#1

Unable to think of a logic. Can I get a hint or a logic

Sanket has a string consisting of only ‘a’ and ‘b’ as the characters. Sanket describes perfectness of a string as the maximum length substring of equal characters. Sanket is given a number k which denotes the maximum number of characters he can change. Find the maximum perfectness he can generate by changing no more than k characters.

Input Format
The first line contains an integer denoting the value of K. The next line contains a string having only ‘a’ and ‘b’ as the characters.

Constraints
2 ≤ N ≤ 10^5

Output Format
A single integer denoting the maximum perfectness achievable.

Sample Input
2
abba

Sample Output
4

#2

@vikanshu2016 This problem can be solved with help of two pointers. Let the first pointer is l and the second pointer is r. Then for every position l we will move right end r until on the substring si.si + 1… sr it is possible to make no more than k swaps to make this substring perfect. Then we need to update the answer with length of this substring and move l to the right.