Stackoverflow: http://stackoverflow.com/questions/20104428/palindrome-count-in-a-string Palindrome count Problem: Given a string S, count the number of non empty sub strings that are palindromes. A sub string is any continuous sequence of characters in the string. A string is said to be palindrome, if the reverse of the string is same as itself.…

palindrome_count_string.rb

require 'benchmark'

def my_method
  string = 'dskjkd'
  chars = string.split('')
  counts = chars.count
  (2..chars.count).each do |len|
    chars.combination(len).each do |comb|
      string = comb.inject(:<<)
      counts += 1 if string.reverse == string
    end
  end
  counts
end

def first_method
  string = 'dskjkd'

  b = string.chars
  (1..b.size).reduce(0) {|t,n| t + b.each_cons(n).reduce(0) \
    {|r,e| w = e.join; w==w.reverse ? r + 1 : r}}
end

def second_method
  string = 'dskjkd'
  count = 0
  len = string.length

  (0..len-1).each do |i|
    (i..len-1).each do |j|
      temp = string[i..j]
      count = count + 1 if temp == temp.reverse
    end
  end
  count
end

def another_method
  string = 'dskjkd'
  counter = 0
  0.upto(string.size).count do |i|
    1.upto(string.size-i) do |j|
      counter +=1 if string[i,j] == string[i,j].reverse
    end
  end
  counter
end

def modified_another_method
  string = 'dskjkd'
  counter = 0
  0.upto(string.length).count do |i|
    1.upto(string.length-i) do |j|
      counter +=1 if string[i,j] == string[i,j].reverse
    end
  end
  counter
end

n = 50000
Benchmark.bm(40) do |x|
  x.report("my_method               "){ n.times { my_method } }
  x.report("first_method            "){ n.times { first_method } }
  x.report("second_method           "){ n.times { second_method } }
  x.report("another_method          "){ n.times { another_method } }
  x.report("modified_another_method "){ n.times { modified_another_method } }
end



Result:

                                               user     system      total        real
my_method                                  5.110000   0.000000   5.110000 (  5.125335)
first_method                               1.830000   0.000000   1.830000 (  1.831094)
second_method                              0.700000   0.000000   0.700000 (  0.706289)
another_method                             0.660000   0.000000   0.660000 (  0.664706)
modified_another_method                    0.670000   0.000000   0.670000 (  0.663622)