#167

Two Sum II - Input Array Is Sorted

Medium
ArrayTwo PointersBinary Search

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.

Examples

Example 1
Input: numbers = [2,7,11,15], target = 9
Output: [1,2]
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]
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]
The sum of -1 and 0 is -1. Therefore index1 = 1, index2 = 2. We return [1, 2].

Constraints

  • 2 <= numbers.length <= 3 * 10^4
  • -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.
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