001. two sum

class :
    def twoSum(self, nums, target):
        for i in range(len(nums)):
            for j in range(i+1,len(nums)):
                if nums[i] + nums[j] == target:
                    return [i,j]

class :
    def twoSum(self, nums, target): 
        dictionary = dict([(y,x) for x,y in enumerate(nums)])
        for i in range(len(nums)):
            x = nums[i]
            if target-x in dictionary and dictionary[target-x] != i:
                return (dictionary[target-x],i)

class :
    def twoSum(self, nums, target): 
        dict = {}
        for i in range(len(nums)):
            x = nums[i]
            if target-x in dict:
                return (dict[target-x],i)
            dict[x] = i