[LC] 167. Two Sum II - Input array is sorted

Posted 2021-03-25 xuanlu

Given an array of integers that is already sorted in ascending order, 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.

Note:

• Your returned answers (both index1 and index2) are not zero-based.
• You may assume that each input would have exactly one solution and you may not use the same element twice.

Example:

Input: numbers = [2,7,11,15], target = 9
Output: [1,2]
Explanation: The sum of 2 and 7 is 9. Therefore index1 = 1, index2 = 2.

 1 class Solution:
 2     def twoSum(self, numbers: List[int], target: int) -> List[int]:
 3         my_dict = {}
 4         for i, num in enumerate(numbers):
 5             remain = target - num
 6             if remain in my_dict:
 7                 index = my_dict[remain]
 8                 return [index, i + 1]
 9             my_dict[num] = i + 1
10         return [-1, -1]