167. 两数之和 II - 输入有序数组

由于数组有序，并且题目保证只有一组解，所以二分和双指针都可以

双指针做法

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

二分

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