[leetcode]Two Sum II – Input array is sorted

For this problem I used binary search, since the array is sorted. A better approach would be to use two pointers (left and right) moving inward. I recall seeing this problem before in “The Beauty of Programming” or “Erta to Offer”.

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class Solution {
public:
    vector<int> result;
    
    void bSearch(vector<int>& numbers, int start, int end, int find) {
        if (start > end) return;
        int middle = (start + end) / 2;
        if (find == numbers[middle]) {
            result.push_back(middle + 1);
            return;
        } else if (find > numbers[middle]) {
            bSearch(numbers, middle + 1, end, find);
        } else {
            bSearch(numbers, start, middle - 1, find);
        }
    }
    
    vector<int> twoSum(vector<int>& numbers, int target) {
        for (int i = 0; i < numbers.size(); i++) {
            int find = target - numbers[i];
            result.push_back(i + 1);
            bSearch(numbers, i + 1, numbers.size(), find);
            if (result.size() == 2) {
                return result;
            }
            result.clear();
        }
        return result;
    }
};