_167.java

package com.fishercoder.solutions;

/**
 * 167. 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.
 * Please note that your returned answers (both index1 and index2) are not zero-based.
 * You may assume that each input would have exactly one solution.

 Input: numbers={2, 7, 11, 15}, target=9
 Output: index1=1, index2=2
 */

public class _167 {

    public int[] twoSum(int[] numbers, int target) {
        int left = 0;
        int right = numbers.length - 1;
        while (left < right) {
            long sum = numbers[left] + numbers[right];
            if (sum > target) {
                right--;
            } else if (sum < target) {
                left++;
            } else {
                int[] res = new int[2];
                res[0] = left + 1;
                res[1] = right + 1;
                return res;
            }
        }
        return new int[]{-1, -1};
    }

}