mirror of
https://github.com/krahets/hello-algo.git
synced 2024-12-26 14:16:28 +08:00
e720aa2d24
* Sync recent changes to the revised Word. * Revised the preface chapter * Revised the introduction chapter * Revised the computation complexity chapter * Revised the chapter data structure * Revised the chapter array and linked list * Revised the chapter stack and queue * Revised the chapter hashing * Revised the chapter tree * Revised the chapter heap * Revised the chapter graph * Revised the chapter searching * Reivised the sorting chapter * Revised the divide and conquer chapter * Revised the chapter backtacking * Revised the DP chapter * Revised the greedy chapter * Revised the appendix chapter * Revised the preface chapter doubly * Revised the figures
42 lines
1.1 KiB
Python
42 lines
1.1 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]:
|
|
"""方法一：暴力枚举"""
|
|
# 两层循环，时间复杂度为 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]:
|
|
"""方法二：辅助哈希表"""
|
|
# 辅助哈希表，空间复杂度为 O(n)
|
|
dic = {}
|
|
# 单层循环，时间复杂度为 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 ======
|
|
# 方法一
|
|
res: list[int] = two_sum_brute_force(nums, target)
|
|
print("方法一 res =", res)
|
|
# 方法二
|
|
res: list[int] = two_sum_hash_table(nums, target)
|
|
print("方法二 res =", res)
|