[leetcode]167. Two Sum II - Input array is sorted

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.

Note:

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.
Example:

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.

二分法的变种

var twoSum = function(numbers, target) {
    var low = 0, high = numbers.length-1
    while(low < high){
        var ret = numbers[low] + numbers[high];
        var diff = ret - target
        if(diff == 0){
            return [low+1, high+1]
        }else if(diff > 0){
            high--
        }else{
            low++
        }
    }
    return []
    
};