58 lines
1.4 KiB
Ruby
58 lines
1.4 KiB
Ruby
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# frozen_string_literal: true
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# Given an array nums of size n, return the majority element.
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# The majority element appears more than n/2 times
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# Time: O(n)
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# Space: O(1)
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module Arrays
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def self.majority_element(nums)
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candidate, count = find_candidate(nums)
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count.positive? ? candidate : nil
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end
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def self.find_candidate(nums)
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candidate = nil
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count = 0
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nums.each do |num|
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candidate, count = update_candidate(candidate, count, num)
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end
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[candidate, count]
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end
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def self.update_candidate(candidate, count, num)
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if count.zero?
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candidate = num
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count = 1
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elsif candidate == num
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count += 1
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else
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count -= 1
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end
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[candidate, count]
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end
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end
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RSpec.describe Arrays do
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describe '.majority_element' do
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it 'returns the majority element in the array' do
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expect(Arrays.majority_element([3, 2, 3])).to eq(3)
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expect(Arrays.majority_element([2, 2, 1, 1, 1, 2, 2])).to eq(2)
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end
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it 'handles different input sizes' do
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expect(Arrays.majority_element([1])).to eq(1)
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expect(Arrays.majority_element([1, 1])).to eq(1)
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expect(Arrays.majority_element([1, 2, 2])).to eq(2)
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expect(Arrays.majority_element([3, 3, 4, 2, 4, 4, 2, 4, 4])).to eq(4)
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end
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it 'handles negative numbers' do
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expect(Arrays.majority_element([-1, -1, -1, 2, 2, 2, -1, -1])).to eq(-1)
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expect(Arrays.majority_element([-3, -2, -3, -3])).to eq(-3)
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end
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end
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end
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