Two Sum II - Input array is sorted - LeetCode -118

 Given an 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 (1-indexed) as an integer array answer of size 2, where 1 <= answer[0] < answer[1] <= numbers.length.

The tests are generated such that there is exactly one solution. You may not use the same element twice.

 

Example 1:

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.

Example 2:

Input: numbers = [2,3,4], target = 6
Output: [1,3]

Example 3:

Input: numbers = [-1,0], target = -1
Output: [1,2]

 Constraints:

• 2 <= numbers.length <= 3 * 104
• -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.

Solution:

Note: Only function is written

class Solution {

    public int[] twoSum(int[] numbers, int target) {

        int a_pointer=0,b_pointer=numbers.length-1;

        

        while(a_pointer <= b_pointer){

            

            int sum = numbers[a_pointer] + numbers[b_pointer];

            

            if(sum>target){

                b_pointer-=1;

            }else if(sum<target){

                a_pointer+=1;

            }else{

                return new int[] {a_pointer+1,b_pointer+1};

            }  

        }

        

         return new int[] {a_pointer+1,b_pointer+1};

    }

}