167. Two Sum II – Input array is sorted

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.

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本题要在一个已排序数组中找两个数，使得这两个数的和等于一个目标target。这应该是LeetCode Two Sum的简化版吧，因为之前那个题有一种解法就是先对数组排序，然后首尾指针夹逼，现在这个题都排好序了，那还有什么好说的呢，直接借用之前的方法。 完整代码如下：

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

本代码提交AC，用时9MS。