TwoSum-LeetCode-Problem_no_1

//  added first solution which I solved last year in O(n2), but now this is of O(n)


class Solution {
    public int[] twoSum(int[] nums, int target) {
        Map<Integer, Integer> nmap = new HashMap<>();
        for(int i=0; i<nums.length ; i++){
            int diff =  target - nums[i];
            if(nmap.containsKey(diff)){
                return new int[]{nmap.get(diff), i};
            }
            // else{
                // else add that key-value pair to map.
                nmap.put(nums[i], i);
            // }
        }
        
        throw new IllegalArgumentException("No match found.");
        
    }
}