Leetcode：Two Sum

Given an array of integers, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution.

Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2

class Solution(object):
    def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        #Time:O(n)
        #Space:O(n)
        dict_num_index = {}
        for i, num in enumerate(nums):
            diff = target - num
            if diff in dict_num_index:
                return [dict_num_index[diff], i + 1]
            ‘‘‘
            if num not in dict_num_index:
                dict_num_index[num] = i + 1
            #return the smallest index of the same value
            ‘‘‘
            dict_num_index[num] = i + 1

时间复杂度：O(n)

空间复杂地：O(n)

注：该串数字可以有重复数值，如果需要返回每个数值最小的index，需要按注释部分编写代码