BROKEN - Broken Keyboard

Bruce Force's keyboard is broken, only a few keys are still working. Bruce has figured out he can still type texts by switching the keyboard layout whenever he needs to type a letter which is currently not mapped to any of the m working keys of the keyboard.

You are given a text that Bruce wishes to type, and he asks you if you can tell him the maximum number of consecutive characters in the text which can be typed without having to switch the keyboard layout. For simplicity, we assume that each key of the keyboard will be mapped to exactly one character, and it is not possible to type other characters by combination of different keys. This means that Bruce wants to know the length of the largest substring of the text which consists of at most m different characters.


The input contains several test cases, each test case consisting of two lines. The first line of each test case contains the number m (1 ≤ m ≤ 128), which specifies how many keys on the keyboard are still working. The second line of each test case contains the text which Bruce wants to type. You may assume that the length of this text does not exceed 1 million characters. Note that the input may contain space characters, which should be handled like any other character.

The last test case is followed by a line containing one zero.


For each test case, print one line with the length of the largest substring of the text which consists of at most m different characters.


This can't be solved by brute force.


hide comments
sumitsinghnit: 2016-08-04 08:35:30

I don't know why but c gave tle, c++5.1 gave runtime error, but finally accepted in c++14 using same code after lot of failed attempts.

Last edit: 2016-08-04 08:36:13
janvijay1997: 2016-06-12 11:32:38

Before taking string as input write char c=getchar(); if constantly getting error !

flyingduchman_: 2016-05-31 20:23:09

never use cin.sync() before getline(cin,str). use getchar() or cin.ignore() instead. Cost me 10+ WA

wewark: 2016-05-18 00:50:20

@piuspbd No, realized that after it cost me 2 WAs

piuspbd: 2016-04-11 14:36:22

Does 'a' == 'A'?

codershinchan: 2015-09-06 19:17:35

"(space)by(space)bru" ,7 characters but consisting of 5 different characters

Last edit: 2015-09-06 19:18:01
hodobox: 2015-09-04 10:01:22

Used strings in c++, 0.22s AC. Don't use vectors, use correct time complexity.

Anubhav Gupta: 2015-01-01 18:00:11

strings are too slow in c++, use vectors

kelaseek: 2014-12-31 08:41:12

"atmost". so you should check "<=" at the end

Adrian Kuegel: 2012-06-11 12:25:08

@Rodolfo: this is a substring which has length 7 and contains only 5 different characters: " by bru". If you see any longer substring with at most 5 different characters, let me know ;-)

Added by:Adrian Kuegel
Time limit:4.358s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ERL JS-RHINO NODEJS PERL6 VB.NET
Resource:University of Ulm Local Contest 2008