1.传统做法是两个指针同时移动，这样的话时间复杂度是o(n)
class Solution(object):
def twoSum(self, numbers, target):
"""
:type numbers: List[int]
:type target: int
:rtype: List[int]
"""
left = 0
right = len(numbers) - 1
while left < right :
if numbers[left] + numbers[right] == target:
return [left+1, right+1]
elif numbers[left] + numbers[right] < target:
left += 1
else:
right -= 1
2.用字典记录下每个number 边记录边判断
···
class Solution(object):
def twoSum(self, numbers, target):
"""
:type numbers: List[int]
:type target: int
:rtype: List[int]
"""
dic = {}
for i,num in enumerate(numbers):
if (target - num) in dic:
return [dic[target - num], i+1]
else:
dic[num] = i+1
···