Longest Run Program In Ruby - ruby

Question

I have a school assignment where i have to find the longest run of adjacent equal characters in a given string with Ruby. My program works fine without the last loop, but once i added it gave me the error:
(repl):47: syntax error, unexpected keyword_end
(repl):53: syntax error, unexpected end-of-input, expecting keyword_end
puts longestRun
^
Here is my Code
puts 'What is your string?'
givenString = gets.chomp
def maxBlock(str)
maxRun = 0
currentRun = 1
characterCounter = 1
if str.length == 0
maxRun = 0
#If no input, longest run is zero
elsif str.length == 1
maxRun = 1
#If string is one character, longest run is 1
elsif str.length == 2 and str[characterCounter] != str[characterCounter + 1]
maxRun = 1
#if string is two chars and they do not equal, longest run is 1
elsif str.length == 3 and str[0] != str[1] and str[1] != str[2]
maxRun = 1
#if string is three chars and they do not equal, longest run is 1
else
str.each_char do|st|
#Go through each char, compare it to the next, find longest run
if st == str[characterCounter]
currentRun++
if currentRun > maxRun
maxRun = currentRun
end
else
currentRun = 1
end
characterCounter++
end
end
end
longestRun = maxBlock(givenString)
puts longestRun
EDIT: I am a highschool student, and only have a base knowledge of programming.
EDIT: I just made a few stupid mistakes. I appreciate everyone's help. Here is my working program without the use of anything too complicated.
puts 'What is your string?'
givenString = gets.chomp
def maxBlock(str)
maxRun = 0
currentRun = 1
characterCounter = 0
if str.length == 0
maxRun = 0
#If no input, longest run is zero
elsif str.length == 1
maxRun = 1
#If string is one character, longest run is 1
elsif str.length == 2 and str[characterCounter] != str[characterCounter + 1]
maxRun = 1
#if string is two chars and they do not equal, longest run is 1
elsif str.length == 3 and str[0] != str[1] and str[1] != str[2]
maxRun = 1
#if string is three chars and they do not equal, longest run is 1
else
characterCounter += 1
str.each_char do|st|
#Go through each char, compare it to the next, find longest run
if st == str[characterCounter]
currentRun += 1
if currentRun > maxRun
maxRun = currentRun
end
else
currentRun = 1
end
characterCounter += 1
end
end
return maxRun
end
longestRun = maxBlock(givenString)
puts longestRun

Answer 1

String Scans and Sorting
There are algorithms for this, but Ruby offers some nice shortcuts. For example:
def longest_string str
str.scan(/((\p{Alnum})\2+)/).collect { |grp1, grp2| grp1 }.sort_by(&:size).last
end
longest_string 'foo baaar quuuux'
#=> "uuuu"
This basically just captures all runs of repeated characters, sorts the captured substrings by length, and then returns the last element of the length-sorted array.
Secondary Sorting
If you want to do a secondary sort, such as first by length and then by alphabetical order, you could replace Enumerable#sort_by with the block form of Enumerable#sort. For example:
def longest_string str
str.scan(/((\p{Alnum})\2+)/).
collect { |grp1, grp2| grp1 }.
sort {|a, b| [a.size, a] <=> [b.size, b] }.
last
end
longest_string 'foo quux baar'
#=> "uu"

Answer 2

This is one way you could do it.
str = "111 wwwwwwwwaabbbbbbbbbbb$$$$****"
r = /
(.) # Match any character in capture group 1
\1* # Match the contents of capture group 1 zero or more times
/x # Free-spacing regex definition mode
str.gsub(r).max_by(&:size)
#=> "bbbbbbbbbbb"
I used the form of String#gsub without a second argument or block, as that returns an enumerator that generates the strings matched by the regex. I then chained that enumerator to the method Enumerable#max_by to find the longest string of consecutive characters. In other words, I used gsub merely to generate matches rather than to perform substitutions.
One could of course write str.gsub(/(.)\1*/).max_by(&:size).

Answer 3

Here is a simplified version that should work in all cases:
puts 'What is your string?'
given_string = gets.chomp
def max_block(str)
max_run = 0
current_run = 1
str.each_char.with_index do |st, idx|
if st == str[idx + 1]
current_run += 1
else
current_run = 1
end
max_run = current_run if current_run > max_run
end
max_run
end
longest_run = max_block(given_string)
puts longest_run
You were on the right track but Ruby can make things a lot easier for you. Notice how with_index gets rid of a lot of the complexity. Iterators, oh yeah.
I also changed your method name and variables to camel_case.
Happy coding!