Description
Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.
Example:
Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
Solution
class Solution:
def twoSum(self, nums, target):
"""
:type nums: List[int]
:type target: int
:rtype: List[int]
"""
buff_dict = {}
if len(nums) <= 1:
return False
for i in range(len(nums)):
if nums[i] in buff_dict.keys():
return [buff_dict[nums[i]], i]
else:
buff_dict[target - nums[i]] = i
备注
该题利用常规枚举思路较为费时O(n^2),标准答案巧用字典数据结构,使时间复杂度降为O(n),即只需扫描一遍数据即可找到对应数对。