1. Two Sum — LeetCode Solution

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

Here is my solution:

class Solution {
    public int[] twoSum(int[] nums, int target) {
        HashMap<Integer, Integer> map = new HashMap<>();
        
        for (int i=0; i<nums.length; i++) {
            int difference = target - nums[i];
            if (map.containsKey(difference)) {
                return new int[] {map.get(difference), i};
            }
            map.put(nums[i], i);
        }
        return new int[] {-1, -1};
    }
}

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