Leet Code 167: Two Sum II - Input Array Is Sorted

Problem statement:

Given a 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. Let these two numbers be numbers[index1] and numbers[index2] where 1 <= index1 < index2 <= numbers.length.

Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2.

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

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:

Copy
/**
 * @param {number[]} numbers
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(numbers, target) {
    let l = 0;
    let r = numbers.length-1;
    while(l<r) {
        if(numbers[l]+numbers[r]===target) {
            return [l+1, r+1];
        } else if(numbers[l]+numbers[r]>target) {
            r--;
        } else {
            l++;
        } 
    }
    return [];
};