44 lines
1.2 KiB
Ruby
44 lines
1.2 KiB
Ruby
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# frozen_string_literal: true
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# Problem Statement: given an array of integers nums and an integer target,
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# return indices of the two numbers such that they add up to target.
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#
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# You may assume that each input would have exactly one solution,
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# and you may not use the same element twice.
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#
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# Input: An array of integers and a target (int)
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# Output: array of indexes of len(2) with sum of element at that index equal to target or nil
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#
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# Time: O(n)
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# Space: O(n)
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module Arrays
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def self.two_sum(nums, target)
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complement_hash = {}
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nums.each_with_index do |num, index|
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complement = target - num
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return [complement_hash[complement], index] if complement_hash.key?(complement)
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complement_hash[num] = index
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end
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nil
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end
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end
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RSpec.describe Arrays do
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describe '.two_sum' do
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it 'returns the correct indices' do
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expect(Arrays.two_sum([2, 7, 11, 15], 9)).to eq([0, 1])
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expect(Arrays.two_sum([3, 2, 4], 6)).to eq([1, 2])
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expect(Arrays.two_sum([3, 3], 6)).to eq([0, 1])
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end
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it 'returns nil if no solution is found' do
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expect(Arrays.two_sum([1, 2, 3, 4], 9)).to be_nil
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expect(Arrays.two_sum([], 5)).to be_nil
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end
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end
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end
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