1.TwoSum.js

/*
========== Question:  =========
167. Two Sum II - Input Array Is Sorted

========== Description: =========== 
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.

Your solution must use only constant extra space.

========== 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. We return [1, 2].
*/

var twoSum = function(numbers, target) {
    let l = 0;
    let r = numbers.length - 1;
    for(let i = 0; i <= numbers.length-1; i++) {
        const sum = numbers[l] + numbers[r];
        if(sum === target) return [l+1, r+1];
        else if(sum < target) l++;
        else r--
    }
}

const numbers = [2, 3, 4];
const target = 6;
console.log(twoSum(numbers, target));