https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/description/

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.

程式碼：

class Solution {
public:
    vector<int> twoSum(vector<int>& numbers, int target) {
        int l = 0, r = numbers.size() - 1;
        for(int i = 0; i < numbers.size(); i ++) {
            int sum = numbers[l] + numbers[r];
            if(sum == target) return {l + 1, r + 1};
            else if(sum < target) l ++;
            else r --;
        }
        return {};
    }
};