mirror of
https://github.com/krahets/hello-algo.git
synced 2026-06-15 22:57:48 +08:00
43 lines
1.2 KiB
Python
43 lines
1.2 KiB
Python
"""
|
||
File: two_sum.py
|
||
Created Time: 2022-11-25
|
||
Author: krahets (krahets@163.com)
|
||
"""
|
||
|
||
|
||
def two_sum_brute_force(nums: list[int], target: int) -> list[int]:
|
||
"""方法 1：総当たり列挙"""
|
||
# 2重ループのため、時間計算量は O(n^2)
|
||
for i in range(len(nums) - 1):
|
||
for j in range(i + 1, len(nums)):
|
||
if nums[i] + nums[j] == target:
|
||
return [i, j]
|
||
return []
|
||
|
||
|
||
def two_sum_hash_table(nums: list[int], target: int) -> list[int]:
|
||
"""方法 2：補助ハッシュテーブル"""
|
||
# 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 range(len(nums)):
|
||
if target - nums[i] in dic:
|
||
return [dic[target - nums[i]], i]
|
||
dic[nums[i]] = i
|
||
return []
|
||
|
||
|
||
"""Driver Code"""
|
||
if __name__ == "__main__":
|
||
# ======= Test Case =======
|
||
nums = [2, 7, 11, 15]
|
||
target = 13
|
||
|
||
# ====== Driver Code ======
|
||
# 方法 1
|
||
res: list[int] = two_sum_brute_force(nums, target)
|
||
print("方法1 res =", res)
|
||
# 方法 2
|
||
res: list[int] = two_sum_hash_table(nums, target)
|
||
print("方法2 res =", res)
|