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Branches - Diana #47

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4e00373
will skip nested(s) function for now
dhan0406 Nov 16, 2019
6d40454
need some help with nested and digit_match
dhan0406 Nov 16, 2019
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84 changes: 60 additions & 24 deletions lib/recursive-methods.rb
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Original file line number Diff line number Diff line change
@@ -1,49 +1,85 @@
# Authoring recursive algorithms. Add comments including time and space complexity for each method.

# Time complexity: ?
# Space complexity: ?
require 'pry'
# Time complexity: O(n)
# Space complexity: O(n)
def factorial(n)
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@CheezItMan CheezItMan Dec 18, 2019

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👍

raise NotImplementedError, "Method not implemented"
if n < 0
raise ArgumentError
end
return 1 if n == 0
return n * factorial(n-1)
end

# Time complexity: ?
# Space complexity: ?
# Time complexity: O(n)
# Space complexity: O(n)
# I think this is reversing the string in place?
def reverse(s)
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👍

raise NotImplementedError, "Method not implemented"
return s if s.length <= 1
return reverse(s[1..-1]) + s[0]
end

# Time complexity: ?
# Space complexity: ?
# Time complexity: O(n)
# Space complexity: O(n)
def reverse_inplace(s)
raise NotImplementedError, "Method not implemented"
return s if s.length <= 1
return reverse_inplace(s[1..-1]) + s[0]
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This creates a new array, so it's not in place

end

# Time complexity: ?
# Space complexity: ?
# Time complexity: O(n)
# Space complexity: O(n)
def bunny(n)
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👍

raise NotImplementedError, "Method not implemented"
return n if n == 0
return 2 + bunny(n-1)
end

# Time complexity: ?
# Space complexity: ?
# NOT PASSING TESTS
def nested(s)
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Ok so not implemented

raise NotImplementedError, "Method not implemented"
return true if s.length == 0
# need to check if s = even number of paren-pairs()
# return true if s.length % 2 == 0
end

# Time complexity: ?
# Space complexity: ?
def search(array, value)
raise NotImplementedError, "Method not implemented"
# Time complexity: O(n)
# Space complexity: O(n)
def search(array, value, i = 0)
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👍

return false if i >= array.length
return true if array[i] == value
return search(array, value, i + 1)
end

# Time complexity: ?
# Space complexity: ?
def is_palindrome(s)
raise NotImplementedError, "Method not implemented"
# Time complexity: O(n)
# Space complexity: O(n)
# ONLY PASSING 2 TESTS
def is_palindrome(s, l = 0, r = s.length-1 )
if s[l] == s[r]
return true
else
return false
end

while l < s.length
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You don't need a while if it's recursive.

You can make the base case

return true if i >= r

return is_palindrome(s, l + 1, r - 1)
end
end

# Time complexity: ?
# Space complexity: ?
def digit_match(n, m)
raise NotImplementedError, "Method not implemented"
# NOT PASSING TESTS
def digit_match(n, m, i = -1)
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You can also pull off digits by % 10.

# i want to check each index from the end and keep track of matching values
n = n.to_s
m = m.to_s
tracker = 0

if n[i] == m[i]
tracker += 1
else
tracker += 0
end

return tracker if i < -(n.length)
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If i is less than n's length?


return digit_match(n, m, i - 1)
end
6 changes: 3 additions & 3 deletions test/recursion_writing_test.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -38,7 +38,7 @@
end
end

xdescribe "reverse" do
describe "reverse" do
it "will reverse 'cat'" do
# Arrange
string = "cat"
Expand Down Expand Up @@ -84,7 +84,7 @@
end


xdescribe "reverse_in_place" do
describe "reverse_in_place" do
it "will reverse 'cat'" do
# Arrange
string = "cat"
Expand Down Expand Up @@ -129,7 +129,7 @@
end
end

xdescribe "bunny" do
describe "bunny" do
it "returns 0 for 0 bunnies" do
# Arrange
count = 0
Expand Down