[Leet Code] Two Sum II Input Array Is Sorted

Leetcode: https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/

Problem:

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 1:

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.

Example 2:

Input: numbers = [2,3,4], target = 6
Output: [1,3]

Example 3:

Input: numbers = [-1,0], target = -1
Output: [1,2]

Solution:

class Solution(object):
    def twoSum(self, numbers, target):
        """
        :type numbers: List[int]
        :type target: int
        :rtype: List[int]
        """
        
        l, r = 0, len(numbers) - 1
        
        while l < r:
            curSum = numbers[l] + numbers[r]
            if curSum > target:
                r -= 1
            elif curSum < target:
                l += 1
            else:
                return [l + 1, r + 1]