Lintcode 610. Two Sum - Difference equals to target

Given an array of integers, find two numbers that their difference equals to a target value.
where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are NOT zero-based.

Example

Example 1:

Input: nums = [2, 7, 15, 24], target = 5 
Output: [1, 2] 
Explanation:
(7 - 2 = 5)

Example 2:

Input: nums = [1, 1], target = 0
Output: [1, 2] 
Explanation:
(1 - 1 = 0)

Notice

It's guaranteed there is only one available solution

Code (Java):

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public class Solution {     /**      * @param nums: an array of Integer      * @param target: an integer      * @return: [index1 + 1, index2 + 1] (index1 < index2)      */     public int[] twoSum7(int[] nums, int target) {         int[] ans = new int[2];                   if (nums == null || nums.length < 2) {             return ans;         }           Map<Integer, Integer> map = new HashMap<>();           for (int i = 0; i < nums.length; i++) {             if (map.containsKey(nums[i])) {                 ans[0] = map.get(nums[i]);                 ans[1] = i + 1;                 return ans;             }               map.put(nums[i] + target, i + 1);             map.put(nums[i] - target, i + 1);         }           return ans;     } }