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Leaves - Bri #48

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ea88705
3 problems complete, tests passing
brilatimer Nov 17, 2019
359b9a4
nested and bunny problems working and tested
brilatimer Nov 17, 2019
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82 changes: 62 additions & 20 deletions lib/recursive-methods.rb
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Original file line number Diff line number Diff line change
@@ -1,49 +1,91 @@
# Authoring recursive algorithms. Add comments including time and space complexity for each method.

# Time complexity: ?
# Space complexity: ?
# Time complexity: O(n)
# Space complexity: O(1) because constant is being multiplied (no arrays)
def factorial(n)
raise NotImplementedError, "Method not implemented"
# solve base case
if n < 0
raise ArgumentError
end
if n == 0
return 1
end
if n <= 2
return n
end
return n * factorial(n-1)
end

# Time complexity: ?
# Space complexity: ?
# Time complexity: O(n)
# Space complexity: O(n)
def reverse(s)
raise NotImplementedError, "Method not implemented"
if s.length <= 1
return s
end
return [reverse(s[1, s.length - 1]), s[0]].join
end
# substring on the left, first char on the right, put these into an arry and call .join
# https://apidock.com/ruby/Array/join

# Time complexity: ?
# Space complexity: ?
def reverse_inplace(s)
raise NotImplementedError, "Method not implemented"
# Time complexity: O(n)
# Space complexity: O(1), no additional space used/no new arrays/strings created
def reverse_inplace(s, index = 0)
start_index = index
end_index = s.length - 1 - index

# middle point has been found. this is basecase
if end_index <= start_index
return s
end
# swap start and end elements
temp = s[start_index]
s[start_index] = s[end_index]
s[end_index] = temp

return reverse_inplace(s, index + 1) # this handles swapping middle
end

# Time complexity: ?
# Space complexity: ?
# Time complexity: O(n)
# Space complexity: O(1)
def bunny(n)
raise NotImplementedError, "Method not implemented"
if n < 0
raise ArgumentError
end
if n == 0 # basecase
return n
end
return bunny(n - 1) + 2
end

# Time complexity: ?
# Space complexity: ?
def nested(s)
raise NotImplementedError, "Method not implemented"
# Time complexity: O(n)
# Space complexity: O(1)
def nested(s, index = 0) # initalize index
start_index = index
end_index = s.length - 1 - index
if end_index < start_index
return true
end
if s[start_index] == '(' && s[end_index] == ')'
return nested(s, index + 1)
else
return false
end
end

# Time complexity: ?
# Space complexity: ?
def search(array, value)
raise NotImplementedError, "Method not implemented"
raise NotImplementedError, "Method not implemented"
end

# Time complexity: ?
# Space complexity: ?
def is_palindrome(s)
raise NotImplementedError, "Method not implemented"
raise NotImplementedError, "Method not implemented"
end

# Time complexity: ?
# Space complexity: ?
def digit_match(n, m)
raise NotImplementedError, "Method not implemented"
raise NotImplementedError, "Method not implemented"
end
8 changes: 4 additions & 4 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 Expand Up @@ -164,7 +164,7 @@
end
end

xdescribe "nested" do
describe "nested" do
it "will return true for empystring" do
# Arrange
string = ""
Expand Down