Two Sum

Two Sum

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].

my code：

class Solution:

    def twoSum(self, nums, target):

        """

        :type nums: List[int]

        :type target: int

        :rtype: List[int]

        """

        for i in range(0,len(nums)):

            j = target - nums[i]

            if j in nums[i+1:]:

                return [i,nums.index(j,i+1)]

other：

class Solution(object):

def twoSum(self, nums, target):

if len(nums) <= 1:

return False

buff_dict = {}

for i in range(len(nums)):

            #判断buff_dict中是否有关键字nums[i]

if nums[i] in buff_dict:

return [buff_dict[nums[i]], i]

else:

buff_dict[target - nums[i]] = i

#执行流程

# nums = [1,2,1,3,5]

# target = 5

# 1 不在 buff_dict，buff_dict更新为{4:0}

# 2 不在 buff_dict，buff_dict更新为{4:0，3:1}

# 1 不在 buff_dict，buff_dict更新为{4:2，3:1}

# 3 在 buff_dict，输出[1,3]

class Solution(object):

def twoSum(self, nums, target):

d = {}

        # enumerate() 函数用于将一个可遍历的数据对象(如列表、元组或字符串)组合为一个索引序列，同时列出数据下标和数据

for i, n in enumerate(nums):

m = target - n

if m in d:

return [d[m], i]

else:

d[n] = i