Example: 2SUM - rFronteddu/general_wiki GitHub Wiki

• Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.
• You may assume that each input would have exactly one solution, and you may not use the same element twice.
• You can return the answer in any order.

class Solution {
    public int[] twoSum(int[] nums, int target) {
        if (nums == null) {
                throw new IllegalArumentException("nums is null");
        }

        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < nums.length; i++) {
                int complement = target - nums[i];
                if (map.containsKey(complement)) {
                        return new int[] {map.get(complement), i};
                }
                map.put(nums[i], i);
        }
        throw new IllegalArumentException("No two elements add up to target");
    }
}