LeetCode练习
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练习1
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【题目】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]. 

【答案】

.. code:: python

    class Solution(object):
        def twoSum(self, nums, target):
            if len(nums) <= 1:
                return False
            buff_dict = {}
            for i in range(len(nums)):
                if nums[i] in buff_dict:
                    return [buff_dict[nums[i]], i]
                else:
                    buff_dict[target - nums[i]] = i

【评论】利用构建dict来降低复杂度（因为dict的复杂度为O(1))，空间换取时间，而且写得很机智啊，只要循环一遍就可以了

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