167-Two-Sum-II-Input-array-is-sorted.js

/**
 * https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/description/
 * Difficulty:Easy
 *
 * 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) {

    for (var i = 0; i < numbers.length - 1; i++) {
        for (var j = i + 1; j < numbers.length; j++) {
            if (numbers[i] + numbers[j] === target) return [i + 1, j + 1];
        }
    }
};

// ==========================================

/**
 * 双指针
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function (nums, target) {

    var lo = 0;
    var hi = nums.length - 1;

    while (nums[lo] + nums[hi] !== target) {
        if (nums[lo] + nums[hi] > target) hi--;
        else lo++;
    }
    return [lo + 1, hi + 1];
};

console.log(twoSum([2, 7, 11, 15], 9));