167. Two Sum II - Input array is sorted

Pick One

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

Seen this question in a real interview before? Yes

No
思路：因为是有序数组，可以采用指针对撞的方式，一个从第一个位置开始，另一个从最后一个位置。
AC代码：

class Solution {
public:
    vector<int> twoSum(vector<int>& numbers, int target) {
        int l=0;int r=numbers.size()-1;
        while(l<r){
            if(numbers[l]+numbers[r]==target){
            int res[2]={l+1,r+1};
            return vector<int>(res,res+2);
            
        }
            else if(numbers[l]+numbers[r]<target){
                l++;
            }
            else if(numbers[l]+numbers[r]>target){
                r--;
            }
        }
        
        
    }
};