167 Two Sum II - Input array is sorted-05/17

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 index 1 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.

You can choose to use hashmap but the space complexity is O(n)

so if you use two pointers then the time is O(n) and the space is O(1)

class Solution {
    public int[] twoSum(int[] nums, int target) {
        int[] ans = new int[2];
        int left = 0;
        int right = nums.length - 1;
        while (left < right) {
            if (nums[left] + nums[right] == target) {
                ans[0] = left + 1;
                ans[1] = right + 1;
                break;
            }else if (nums[left] + nums[right] < target) {
                left++;
            } else{
                right--;
            }
        }
        return ans;
    }
}