Two Sum II - Input Array Is Sorted

Two Sum II - Input Array Is Sorted is a Medium Data Structures and Algorithms interview problem you can solve, run and submit on Thita.ai. It belongs to the Two Pointers pattern, in the Converging (Sorted Array Target Sum) subpattern.

Problem statement

Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order, find two numbers such that they add up to a specific target number. Let these two numbers be numbers[index1] and numbers[index2] where 1 <= index1 < index2 <= numbers.length.

Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2.

The tests are generated such that there is exactly one solution. You may not use the same element twice.

Your solution must use only constant extra space.

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. We return [1, 2].

Example 2:

Input: numbers = [2,3,4], target = 6 Output: [1,3] Explanation: The sum of 2 and 4 is 6. Therefore index1 = 1, index2 = 3. We return [1, 3].

Example 3:

Input: numbers = [-1,0], target = -1 Output: [1,2] Explanation: The sum of -1 and 0 is -1. Therefore index1 = 1, index2 = 2. We return [1, 2].

Constraints:

- 2 <= numbers.length <= 3 104

- -1000 <= numbers[i] <= 1000

- numbers is sorted in non-decreasing order.

- -1000 <= target <= 1000

- The tests are generated such that there is exactly one solution.

Topics and companies

Topics: Array, Two Pointers, Binary Search.

Reported in interviews at Amazon, Apple, ByteDance, Expedia, Facebook, Goldman Sachs, Google, Microsoft, Paypal, Wayfair.

How to practise Two Sum II - Input Array Is Sorted on Thita.ai

Starter code is provided in C, C#, C++, Go, Java, JavaScript and Python. Your solution runs against 5 test cases for this problem, with the AI coach available for a hint when you are stuck rather than a finished answer. The reference solution runs in O(n) time and O(1) space.

Open Two Sum II - Input Array Is Sorted in the code editor, or read the Two Sum II - Input Array Is Sorted editorial for a worked solution with its approach and complexity analysis.

Where Two Sum II - Input Array Is Sorted sits in the DSA pattern sheet

Problems related to Two Sum II - Input Array Is Sorted

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