TwoSum_II.js

// Source : https://leetcode.com/problems/two-sum-ii-input-array-is-sorted
// Author : Dean Shi
// Date   : 2017-07-11

/***************************************************************************************
 *
 * 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 and you may not use
 * the same element twice.
 *
 * Input: numbers={2, 7, 11, 15}, target=9
 * Output: index1=1, index2=2
 *
 *
 ***************************************************************************************/

/**
 * @param {number[]} numbers
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(numbers, target) {
    let sum, p1 = 0, p2 = numbers.length - 1

    while ((sum = numbers[p1] + numbers[p2]) !== target) sum < target ? ++p1 : --p2

    return [p1 + 1, p2 + 1]
};