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Longest Sub-string with at most K Distinct Characters

MEDIUM

35 mins

21 upvotes

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Problem

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Longest Sub-string with at most K Distinct Characters

Contributed by

Dhruv Sharma

Last Updated: 23 Feb, 2023

Medium

0/80

Avg time to solve 35 mins

Success Rate 65 %

21 upvotes

Problem Statement

You are given string S of length N, and an integer K. Your task is to find the length of the longest substring that contains at most K distinct characters.

Detailed explanation ( Input/output format, Notes, Images )

Input Format:

The first line contains an Integer 'T' which denotes the number of test cases/queries to be run. 
Then the test cases follow. 

The first line of input for each test case/query contains an integer K.

The second line of input for each test case/query contains a string S.

Output Format:

For each test case, print the length of the longest substring that contains at most K distinct characters.

Output for every test case will be printed in a separate line.

Note:

You do not need to print anything, it has already been taken care of. Just implement the function.

Constraints:

1 <= T <= 10
1 <= K <= 26
1 <= N <= 10^4

Time Limit: 1sec

Sample Input 1:

2
2
abcba
1
abccc

Sample Output 1:

3
3

Explanation of the Sample Input1:

Test Case 1:
K = 2 in the first test case so we can choose substring ‘bcb’ having 2 distinct characters which are less than equal to K=2. 
We cannot get any other substring of length 4 or greater having distinct characters less than equal to 2.
Test Case 2:
K = 1 in the second test case so we can choose substring ‘ccc’ having only 1 distinct character which is less than equal to K=1. 
We cannot get any other substring of length 4 or greater having distinct characters less than equal to 1.

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