leetcode 1.两数之和（重刷）

暴力解法：

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


        

空间换时间：哈希表

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        # 创建一个空字典，用来做"空间换时间"
        # 格式为 {数字: 这个数字对应的索引}
        hash_map = {}

        for i in range(len(nums)):
            current_num = nums[i]

            complement = target-nums[i]

            if complement in hash_map:
                return [hash_map[complement],i]
            
            hash_map[current_num] = i