two_sum2.go

/*
167. Two Sum II - Input array is sorted
https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/

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:

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.
*/

package twosum2

func twoSum2(numbers []int, target int) []int {
	n := len(numbers)
	var (
		l = 0
		r = n - 1
	)

	for l < r {
		if numbers[l]+numbers[r] == target {
			return []int{l + 1, r + 1}
		} else if numbers[l]+numbers[r] < target {
			l++
		} else {
			r--
		}
	}
	panic("The input has no solution.")
}