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Two Sum II - Optimal Target Pair

Given an 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. Return the indices of the two numbers, `[index1, index2]`, as an integer array of length 2 where `1 <= index1 < index2 <= numbers.length`. Your solution must use only **O(1) extra space**.

Examples:
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].
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].
Constraints:
  • 2 <= numbers.length <= 3 * 10^4
  • -1000 <= numbers[i] <= 1000
  • numbers is sorted in non-decreasing order.
  • The tests are generated such that there is exactly one solution.
#Hash Table#Two Pointers#Array
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