Problem

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.

Code

static int var = [](){
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();
class Solution {
public:
    vector<int> twoSum(vector<int>& numbers, int target) {
        vector<int> res;
        int i = 0,j=numbers.size()-1;
        int tmp = 0;
        while((tmp=numbers[i]+numbers[j])!=target){
            if(tmp>target)
                j--;
            if(tmp<target)
                i++;
        }
        res.push_back(i+1);
        res.push_back(j+1);
        return res;
    }
};

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