Created
December 30, 2014 23:49
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Pallindromes
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class String | |
def pallindrome? | |
string = self.downcase.gsub(/[^0-9a-z]/i,'') | |
return false if string.length <= 1 | |
string.reverse == string | |
end | |
def collect_possible_starts_and_end | |
#{ a: [0, 1], b: [3], c: [1,4,6]} | |
return if @pallindrome_char_instances if @pallindrome_char_instances | |
@pallindrome_char_instances = {} | |
for i in (0..self.length-1) | |
if @pallindrome_char_instances.has_key?(self[i]) | |
@pallindrome_char_instances[self[i]] << i | |
else | |
@pallindrome_char_instances[self[i]] = [i] | |
end | |
end | |
@pallindrome_char_instances | |
end | |
def find_pallindromes | |
possibles = collect_possible_starts_and_end | |
pallindromes =[] | |
for key in possibles.keys | |
indexes = possibles[key] | |
if indexes.length > 1 | |
for start_i in indexes | |
for end_i in indexes | |
pallindromes << self[start_i..end_i] unless !self[start_i..end_i].pallindrome? | |
end | |
end | |
end | |
end | |
pallindromes | |
end | |
def extract_pallindrome | |
find_pallindromes.last | |
end | |
end |
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require "rspec" | |
require_relative "pallindrome" | |
describe "#pallindrome?" do | |
context "when given a string containing a pallindrome" do | |
it "returns true when it is a pallindrome" do | |
expect("aba".pallindrome?).to be(true) | |
expect("moom".pallindrome?).to be true | |
expect("qamoomaq".pallindrome?).to be true | |
expect("qamoaomaq".pallindrome?).to be true | |
expect("civic".pallindrome?).to be true | |
expect("cdr".pallindrome?).to be false | |
end | |
it "allows mixed case pallindromes" do | |
expect("QAmoaomAq".pallindrome?).to be true | |
expect("qaMOAOMaQ".pallindrome?).to be true | |
end | |
it "ignores whitespace" do | |
expect("A slut nixes sex in Tulsa".pallindrome?).to be true | |
end | |
it "ignores punctuation" do | |
expect("A car, a man, a maraca.".pallindrome?).to be true | |
expect("Cigar? Toss it in a can. It is so tragic.".pallindrome?).to be true | |
end | |
it "it should be case insensititve" do | |
expect("Aba".pallindrome?).to be(true) | |
end | |
it "should not care about non-alphanumerics" do | |
expect("a b, a".pallindrome?).to be(true) | |
end | |
end | |
context "with a string that is not a pallindrome" do | |
it "returns false" do | |
expect("cdr".pallindrome?).to eq(false) | |
expect("".pallindrome?).to be false | |
expect(".?.".pallindrome?).to be false | |
expect(".i.".pallindrome?).to be false | |
expect(".iaI.".pallindrome?).to be true | |
end | |
end | |
end | |
describe "#find_pallindromes" do | |
context "with a string containing at least one pallindrome" do | |
it "should find pallindromes in a sentence" do | |
expect("aba hello".find_pallindromes).to include("aba") | |
end | |
it "should find pallindromes in a sentence" do | |
expect("aba hello".find_pallindromes).to include("aba") | |
end | |
it "extracts pallindromes from a string" do | |
expect("a moom".find_pallindromes).to eq ['moom', 'oo'] | |
expect("aba Cain: a maniac.".find_pallindromes).to eq ["aba", "a Ca", "ain: a mania", "a ma", "in: a mani", "n: a man"] | |
expect("a radar".find_pallindromes).to eq ["a ra", "ada", "radar"] | |
expect("aba hello".find_pallindromes).to eq ["aba", "ll"] | |
expect("Amy, must I jujitsu my ma?".find_pallindromes).to eq ["my, m", "my, must I jujitsu my m", "must I jujitsu m", "my m", "y, must I jujitsu my", "ust I jujitsu", "st I jujits", "t I jujit", "juj"] | |
end | |
it "should return an empty array when no pallindromes are present" do | |
expect("no palies".find_pallindromes.length).to eq(0) | |
end | |
end | |
end |
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