/**
 * 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.
 *
 * Time complexity: O(n)
 * Memory complexity: O(1)
 */
public class TwoSumII {
    public int[] twoSum(int[] numbers, int target) {
        int l = 0, r = numbers.length - 1;
        while (l < r) {
            int sum = numbers[l] + numbers[r];
            if (sum == target) return new int[] {l + 1, r + 1};
            else if (sum < target) l++;
            else r++;
        }
        return new int[]{};
    }
}
