#1 Two Sum.java

//https://leetcode.com/problems/two-sum/
class Solution {
    public int[] twoSum(int[] nums, int target) {
        HashMap<Integer,Integer> map = new HashMap<>();
        for(int i = 0 ; i < nums.length ; i++) {
            if(map.containsKey(target - nums[i])) {
                return new int[] {map.get(target - nums[i]) , i};
            }
            else {
                map.put(nums[i],i);
            }
        }
        return null;
    }
}