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Daniela Sanchez - Leaves #23

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@dnsanche dnsanche commented Sep 23, 2019 •
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Will answer these questions later as I need to head out!

Sorting & Reverse Sentence

Question Answer
Describe how Bubble Sort works Bubble sorts goes through the array and compares the first element with the next one, if it the first element is bigger than the second one it swaps it, then, it compares again the element swapped with the element next to it. If the the element to the right is bigger, it stops the swap and starts again from the begging of the array.
Describe how Selection Sort works It starts by defining that the current minimum is the first element and then, it goes through the whole array checking if there is another index with a lowest value. If another minimum is found, it swaps it with the current minimum. Then, the current minimum becames the values of the next index and it scans again the array to see if there is a value lower than the current minimum. If there is not, it leaves it as it is and sets the current minimum to the next index and repeats.
Describe how Insertion sort works Starts with the first element of the array (index = 0) and it compares it with the element of the left. If there is no item, it moves to next index and compares it with the elements of the left. If this element is lower, it swaps it and moves to the next index, it compares this element with the elements of the left and swaps it if it founds a bigger element until it reaches the beginning of the array. Then, moves to the next index and repeats.
Which Sorting Algorithm has the best time complexity? Merge sort is better if the size of the array is big, but if the array is small, insertions sort is faster.
 

CheezItMan
CheezItMan reviewed Oct 9, 2019
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Well done. You hit the learning goals here. Nice work!

lib/reverse_sentence.rb
Comment on lines +2 to +3
# Time complexity: O(n), because we check at most 2 times each character.
# Space complexity: O(1), variables are always constant.
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Well done

lib/reverse_sentence.rb
reverse(my_sentence, first ,my_sentence.length - 1)
end

def reverse(string,first,last)
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Very good helper method

lib/sort_by_length.rb
# Space complexity: ?
# Time complexity: O(n^2) as there are two loops that depend on the size of the elements.
# Space complexity: O(n) as I'm creating a new array.
def sort_by_length(my_sentence)
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nicely done insertion sort.

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