class Solution:
    def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        
        # 暴力检索, 复杂度 O(n*2)
        # for i in range(0, len(nums)):
        #     for j in range(i+1, len(nums)):
        #         if nums[i] + nums[j] == target:
        #             return [i, j]
        
        # 通过dict，复杂度变成 O(n)
        hash_map = dict()
        for index, num in enumerate(nums):
            another_num = target - num
            if another_num in hash_map:
                return [hash_map[another_num], index]
            hash_map[num] = index