mirror of
https://github.com/krahets/hello-algo.git
synced 2026-06-15 22:57:48 +08:00
47 lines
1.0 KiB
Ruby
47 lines
1.0 KiB
Ruby
=begin
|
||
File: two_sum.rb
|
||
Created Time: 2024-04-09
|
||
Author: Blue Bean (lonnnnnnner@gmail.com)
|
||
=end
|
||
|
||
### 方法1：総当たり列挙 ###
|
||
def two_sum_brute_force(nums, target)
|
||
# 2重ループのため、時間計算量は O(n^2)
|
||
for i in 0...(nums.length - 1)
|
||
for j in (i + 1)...nums.length
|
||
return [i, j] if nums[i] + nums[j] == target
|
||
end
|
||
end
|
||
|
||
[]
|
||
end
|
||
|
||
### 方法2：補助ハッシュテーブル ###
|
||
def two_sum_hash_table(nums, target)
|
||
# 補助ハッシュテーブルを使用し、空間計算量は O(n)
|
||
dic = {}
|
||
# 単一ループで、時間計算量は O(n)
|
||
for i in 0...nums.length
|
||
return [dic[target - nums[i]], i] if dic.has_key?(target - nums[i])
|
||
|
||
dic[nums[i]] = i
|
||
end
|
||
|
||
[]
|
||
end
|
||
|
||
### Driver Code ###
|
||
if __FILE__ == $0
|
||
# ======= Test Case =======
|
||
nums = [2, 7, 11, 15]
|
||
target = 13
|
||
|
||
# ====== Driver Code ======
|
||
# 方法 1
|
||
res = two_sum_brute_force(nums, target)
|
||
puts "方法1 res = #{res}"
|
||
# 方法 2
|
||
res = two_sum_hash_table(nums, target)
|
||
puts "方法2 res = #{res}"
|
||
end
|