two-sum-ii-input-array-is-sorted.cpp

// 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.
//


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