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47 lines
984 B
47 lines
984 B
=begin
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File: two_sum.rb
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Created Time: 2024-04-09
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Author: Blue Bean (lonnnnnnner@gmail.com)
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=end
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### 方法一：暴力列舉 ###
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def two_sum_brute_force(nums, target)
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# 兩層迴圈，時間複雜度為 O(n^2)
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for i in 0...(nums.length - 1)
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for j in (i + 1)...nums.length
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return [i, j] if nums[i] + nums[j] == target
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end
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end
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[]
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end
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### 方法二：輔助雜湊表 ###
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def two_sum_hash_table(nums, target)
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# 輔助雜湊表，空間複雜度為 O(n)
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dic = {}
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# 單層迴圈，時間複雜度為 O(n)
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for i in 0...nums.length
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return [dic[target - nums[i]], i] if dic.has_key?(target - nums[i])
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dic[nums[i]] = i
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end
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[]
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end
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### Driver Code ###
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if __FILE__ == $0
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# ======= Test Case =======
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nums = [2, 7, 11, 15]
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target = 13
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# ====== Driver Code ======
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# 方法一
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res = two_sum_brute_force(nums, target)
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puts "方法一 res = #{res}"
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# 方法二
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res = two_sum_hash_table(nums, target)
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puts "方法二 res = #{res}"
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end
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