Created
January 25, 2016 00:44
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| =begin | |
| Given an array of positive integers, find all pairs that have a difference of a specified value k. | |
| Pass: O(n^2) | |
| Super Extra Credit: O(n) | |
| =end | |
| # O(n^2) Solution | |
| def difference_pairs(array, k) | |
| # uniq is O(n), or you can implement one using a Hash | |
| array.uniq! | |
| results = [] | |
| # test every combination of integers using a nested iterators O(n^2) | |
| array.each_with_index do |first, first_index| | |
| array[first_index+1..-1].each_with_index do |second, second_index| | |
| difference = (first - second).abs | |
| results << [first, second] if difference == k | |
| end | |
| end | |
| return results | |
| end | |
| p difference_pairs([1, 9, 4, 2, 2, 4, 3, 8], 5) | |
| # O(n) Solution | |
| def difference_pairs(array, k) | |
| # implementing uniq in-house O(n) | |
| unique = {} | |
| array.each do |num| | |
| unique[num] = num | |
| end | |
| results = [] | |
| # instead of checking a - b = diff, we check if diff + b = a | |
| # i.e., we check if a exists in the hash | |
| unique.each do |key, value| | |
| results << [value, unique[k + value]] if unique[k + value] | |
| end | |
| return results | |
| end | |
| p difference_pairs([1, 9, 4, 2, 2, 4, 3, 8], 5) |
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