https://leetcode.com/problems/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.

解题思路：

很简单，几乎没什么可说的。

对于已经排序的数组，two pointers分别指向头尾。

class Solution { public int[] twoSum(int[] numbers, int target) { int start = 0, end = numbers.length - 1; int[] res = new int[2]; while (start < end) { if (numbers[start] + numbers[end] == target) { res[0] = start + 1; res[1] = end + 1; return res; } else if (numbers[start] + numbers[end] < target) { start++; } else { end--; } } return res; } }

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.