Two Sum II Input Array Is Sorted
Given a 1-indexed array of integers numbers that is sorted in non-decreasing order, find two numbers such that they add up to a specific target number.
Return the indices of the two numbers (1-indexed) as an array of size 2.
You may assume that each input has exactly one solution, and you may not use the same element twice.
Your solution must use only constant extra space.
Example 1
Input
4 2 7 11 15 9
Output
1 2
Explanation
The numbers at indices 1 and 2 are 2 and 7.
Their sum is 9, so the answer is [1, 2].
Example 2
Input
3 2 3 4 6
Output
1 3
Explanation
The numbers at indices 1 and 3 are 2 and 4.
Their sum is 6, so the answer is [1, 3].
Constraints
Hints:
Hint 1
Since the array is already sorted, use one pointer at the beginning and another at the end.
Hint 2
If the current sum is smaller than the target, move the left pointer forward. If the current sum is larger than the target, move the right pointer backward until the target sum is found.
Follow-up
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Author & Technical Reviewer
Technically reviewed by: ExamAdda Technical Review Team
Technical Reviewers, ExamAdda
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Published
Aug 4, 2026
Last updated
Aug 6, 2026
Content Verification Methodology
Definitions and complexity claims were checked against authoritative computer-science references. Code examples were compiled and tested with standard, boundary and edge-case inputs.
Expected Output