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Heather #15

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5da2f0b
added grouped_anagrams method
piffer59 Sep 14, 2019
aefbd2a
top_k method
piffer59 Sep 17, 2019
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62 changes: 53 additions & 9 deletions lib/exercises.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -2,29 +2,73 @@

# This method will return an array of arrays.
# Each subarray will have strings which are anagrams of each other
# Time Complexity: ?
# Space Complexity: ?
# Time Complexity: Would this by O(nlog n) for sorting of the string?
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I would say O( n * m log m) where n is the number of words, and m the length of each word. If you can assume that the words are small, then you could say this is O(n)

# Space Complexity: O(n + m), n is the size of the array and m is the size of the hash
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Since the size of the hash depends on the size of strings I would say O(n)


def grouped_anagrams(strings)
raise NotImplementedError, "Method hasn't been implemented yet!"
if strings == []
return []
end

word_hash = {}

strings.each do |word|
sorted_word = word.chars.sort.join
if word_hash[sorted_word]
word_hash[sorted_word] << word
else
word_hash[sorted_word] = [word]
end
end

return word_hash.values
end

# This method will return the k most common elements
# in the case of a tie it will select the first occuring element.
# Time Complexity: ?
# Space Complexity: ?
# Time Complexity: O(nlog n) because of the sorted array is at least
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True! Could this be faster without sorting?

# Space Complexity: O(n), which ever takes up more space, the freq_hash (likely this one) or the sorted frequencies
def top_k_frequent_elements(list, k)
raise NotImplementedError, "Method hasn't been implemented yet!"
end
if list == [] || k == 0
return []
end

freq_hash = {}
unique_values = []
max_freq = 0
list.each do |num|
if freq_hash.include?(num)
freq_hash[num] += 1
else
freq_hash[num] = 1
unique_values << num
end
end

sorted_frequencies = freq_hash.values.sort

answer_arr = []
k.times do
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This looks like a loop that runs k times and a nested loop which runs maybe n times.

unique_values.each do |num|
if freq_hash[num] == sorted_frequencies[-1]
answer_arr << num
sorted_frequencies.pop
freq_hash.delete(num)
break
end
end
end

return answer_arr
end

# This method will return the true if the table is still
# a valid sudoku table.
# Each element can either be a ".", or a digit 1-9
# The same digit cannot appear twice or more in the same
# The same digit cannot appear twice or more in the same
# row, column or 3x3 subgrid
# Time Complexity: ?
# Space Complexity: ?
def valid_sudoku(table)
raise NotImplementedError, "Method hasn't been implemented yet!"
end
end
93 changes: 46 additions & 47 deletions test/exercises_test.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@
it "will return [] for an empty array" do
#Arrange
list = []

# Act-Assert
expect(grouped_anagrams(list)).must_equal []
end
Expand All @@ -18,9 +18,9 @@
answer = grouped_anagrams(list)

expected_answer = [
["ate","eat","tea"],
["nat","tan"],
["bat"]
["ate", "eat", "tea"],
["nat", "tan"],
["bat"],
]

# Assert
Expand All @@ -42,7 +42,7 @@
["tar"],
["pop"],
["pan"],
["pap"]
["pap"],
]

# Assert
Expand All @@ -59,7 +59,7 @@
answer = grouped_anagrams(list)

expected_answer = [
[ "aet", "ate", "eat", "eta", "tae", "tea"]
["aet", "ate", "eat", "eta", "tae", "tea"],
]
# Assert
answer.each_with_index do |array, index|
Expand All @@ -68,17 +68,17 @@
end
end

xdescribe "top_k_frequent_elements" do
describe "top_k_frequent_elements" do
it "works with example 1" do
# Arrange
list = [1,1,1,2,2,3]
list = [1, 1, 1, 2, 2, 3]
k = 2

# Act
answer = top_k_frequent_elements(list, k)

# Assert
expect(answer.sort).must_equal [1,2]
expect(answer.sort).must_equal [1, 2]
end

it "works with example 2" do
Expand Down Expand Up @@ -128,22 +128,21 @@
# Assert
expect(answer.sort).must_equal [1]
end

end

xdescribe "valid sudoku" do
it "works for the table given in the README" do
# Arrange
table = [
["5","3",".",".","7",".",".",".","."],
["6",".",".","1","9","5",".",".","."],
[".","9","8",".",".",".",".","6","."],
["8",".",".",".","6",".",".",".","3"],
["4",".",".","8",".","3",".",".","1"],
["7",".",".",".","2",".",".",".","6"],
[".","6",".",".",".",".","2","8","."],
[".",".",".","4","1","9",".",".","5"],
[".",".",".",".","8",".",".","7","9"]
["5", "3", ".", ".", "7", ".", ".", ".", "."],
["6", ".", ".", "1", "9", "5", ".", ".", "."],
[".", "9", "8", ".", ".", ".", ".", "6", "."],
["8", ".", ".", ".", "6", ".", ".", ".", "3"],
["4", ".", ".", "8", ".", "3", ".", ".", "1"],
["7", ".", ".", ".", "2", ".", ".", ".", "6"],
[".", "6", ".", ".", ".", ".", "2", "8", "."],
[".", ".", ".", "4", "1", "9", ".", ".", "5"],
[".", ".", ".", ".", "8", ".", ".", "7", "9"],
]

# Act
Expand All @@ -156,15 +155,15 @@
it "fails for the table given in the README" do
# Arrange
table = [
["8","3",".",".","7",".",".",".","."],
["6",".",".","1","9","5",".",".","."],
[".","9","8",".",".",".",".","6","."],
["8",".",".",".","6",".",".",".","3"],
["4",".",".","8",".","3",".",".","1"],
["7",".",".",".","2",".",".",".","6"],
[".","6",".",".",".",".","2","8","."],
[".",".",".","4","1","9",".",".","5"],
[".",".",".",".","8",".",".","7","9"]
["8", "3", ".", ".", "7", ".", ".", ".", "."],
["6", ".", ".", "1", "9", "5", ".", ".", "."],
[".", "9", "8", ".", ".", ".", ".", "6", "."],
["8", ".", ".", ".", "6", ".", ".", ".", "3"],
["4", ".", ".", "8", ".", "3", ".", ".", "1"],
["7", ".", ".", ".", "2", ".", ".", ".", "6"],
[".", "6", ".", ".", ".", ".", "2", "8", "."],
[".", ".", ".", "4", "1", "9", ".", ".", "5"],
[".", ".", ".", ".", "8", ".", ".", "7", "9"],
]

# Act
Expand All @@ -177,15 +176,15 @@
it "fails for a duplicate number in a sub-box" do
# Arrange
table = [
["5","3",".",".","7",".",".",".","."],
["6",".","3","1","9","5",".",".","."],
[".","9","8",".",".",".",".","6","."],
["8",".",".",".","6",".",".",".","3"],
["4",".",".","8",".","3",".",".","1"],
["7",".",".",".","2",".",".",".","6"],
[".","6",".",".",".",".","2","8","."],
[".",".",".","4","1","9",".",".","5"],
[".",".",".",".","8",".",".","7","9"]
["5", "3", ".", ".", "7", ".", ".", ".", "."],
["6", ".", "3", "1", "9", "5", ".", ".", "."],
[".", "9", "8", ".", ".", ".", ".", "6", "."],
["8", ".", ".", ".", "6", ".", ".", ".", "3"],
["4", ".", ".", "8", ".", "3", ".", ".", "1"],
["7", ".", ".", ".", "2", ".", ".", ".", "6"],
[".", "6", ".", ".", ".", ".", "2", "8", "."],
[".", ".", ".", "4", "1", "9", ".", ".", "5"],
[".", ".", ".", ".", "8", ".", ".", "7", "9"],
]

# Act
Expand All @@ -198,15 +197,15 @@
it "fails for a duplicate number in a bottom right sub-box" do
# Arrange
table = [
["5","3",".",".","7",".",".",".","."],
["6",".","2","1","9","5",".",".","."],
[".","9","8",".",".",".",".","6","."],
["8",".",".",".","6",".",".",".","3"],
["4",".",".","8",".","3",".",".","1"],
["7",".",".",".","2",".",".",".","6"],
[".","6",".",".",".",".","2","8","."],
[".",".",".","4","1","9","8",".","5"],
[".",".",".",".","8",".",".","7","9"]
["5", "3", ".", ".", "7", ".", ".", ".", "."],
["6", ".", "2", "1", "9", "5", ".", ".", "."],
[".", "9", "8", ".", ".", ".", ".", "6", "."],
["8", ".", ".", ".", "6", ".", ".", ".", "3"],
["4", ".", ".", "8", ".", "3", ".", ".", "1"],
["7", ".", ".", ".", "2", ".", ".", ".", "6"],
[".", "6", ".", ".", ".", ".", "2", "8", "."],
[".", ".", ".", "4", "1", "9", "8", ".", "5"],
[".", ".", ".", ".", "8", ".", ".", "7", "9"],
]

# Act
Expand All @@ -216,4 +215,4 @@
expect(valid).must_equal false
end
end
end
end