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Leaves - Hallie Johnson #14

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23 changes: 18 additions & 5 deletions lib/max_subarray.rb
Original file line number Diff line number Diff line change
@@ -1,8 +1,21 @@

# Time Complexity: ?
# Space Complexity: ?
# Time Complexity: O(n); it iterates over each element in the nums array once.
# I don't think the max method adds meaningful time complexity. ?

# Space Complexity: O(1); makes the same number of variables regardless of nums size.
# Variables hold a single value and do not scale.
def max_sub_array(nums)
Comment on lines +2 to 7

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👍 Nice!

return 0 if nums == nil

raise NotImplementedError, "Method not implemented yet!"
return if nums == nil || nums.length == 0

max_so_far = nums[0]
max_ending_here = nums[0]
i = 1

while i < nums.length
max_ending_here = [nums[i], max_ending_here + nums[i]].max
max_so_far = [max_so_far, max_ending_here].max
i += 1
end

return max_so_far
end
28 changes: 24 additions & 4 deletions lib/newman_conway.rb
Original file line number Diff line number Diff line change
@@ -1,7 +1,27 @@


# Time complexity: ?
# Space Complexity: ?
# Time complexity: O(n); processes scale based upon num input
# Space Complexity: O(n); space needs are in proportion to num input.
def newman_conway(num)
Comment on lines +3 to 5

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👍

raise NotImplementedError, "newman_conway isn't implemented"
end
sequence = [0, 1, 1]
result = "1 1"
count = 3

if num < 1
raise ArgumentError, "Input must be greater than 0."
elsif num == 1
return "#{sequence[1]}"
elsif num == 2
return result
end

while count <= num
new = sequence[sequence[count - 1]] + sequence[count - sequence[ count - 1]]

sequence << new
result += " #{new}"
count += 1
end

return result
end
52 changes: 26 additions & 26 deletions test/max_sub_array_test.rb
Original file line number Diff line number Diff line change
@@ -1,70 +1,70 @@
require_relative "test_helper"

xdescribe "max subarray" do
describe "max subarray" do
it "will work for [-2,1,-3,4,-1,2,1,-5,4]" do
# Arrange
input = [-2,1,-3,4,-1,2,1,-5,4]

# Act
answer = max_sub_array(input)

# Assert
expect(answer).must_equal 6
end

it "will work with a totally negative array" do
# Arrange
input = [-3, -4, -5, -6, -7]

# Act
answer = max_sub_array(input)

# Assert
expect(answer).must_equal(-3)
end

it "will work with a totally negative array with the largest element at the rear" do
# Arrange
input = [ -4, -5, -6, -7, -3]

# Act
answer = max_sub_array(input)

# Assert
expect(answer).must_equal(-3)
end

it "will work with a 1-element array" do
# Arrange
input = [3]

# Act
answer = max_sub_array(input)

# Assert
expect(answer).must_equal 3
end

it "will return nil for an empty array" do
# Arrange
input = []

# Act
answer = max_sub_array(input)

# Assert
expect(answer).must_be_nil
# Arrange
input = []
# Act
answer = max_sub_array(input)
# Assert
expect(answer).must_be_nil
end

it "will work for [50, -50, 50]" do
# Arrange
input = [50, -50, 50]

# Act
answer = max_sub_array(input)

# Assert
expect(answer).must_equal 50
end

end
end