def twoSum(nums, target):
    sz = len(nums)
    for i in range(sz):
        for j in range(i):
            if nums[i] + nums[j] == target:
                return {i, j}


def twoSumDict(nums, target):
    # 用len()方法取得nums列表长度
    n = len(nums)
    # 创建一个空字典
    d = {}
    for x in range(n):
        a = target - nums[x]
        # 字典d中存在nums[x]时
        if nums[x] in d:
            return d[nums[x]], x
        # 否则往字典增加键/值对
        else:
            d[a] = x
    # 边往字典增加键/值对，边与nums[x]进行对比


if __name__ == '__main__':
    nums = [2, 4, 6, 7, 1]
    target = 3
    print(twoSumDict(nums, target))