在给定的一些数字中找出两个数，使他们的和为 N
class Solution(object):
def twoSum(self, nums, target):
"""
:type nums: List[int]
:type target: int
:rtype: List[int]
"""
mydict = {}
for i in range(len(nums)):
if target-nums[i] in mydict:
return [i,mydict[target-nums[i]]]
else:
mydict[nums[i]] = i
return
