0001_Two_Sum.java

/*
 * 1. Two Sum
 * Problem Link: https://leetcode.com/problems/two-sum/
 * Difficulty:   Easy
 * 
 * Solution Created by: Muhammad Khuzaima Umair
 * LeetCode : https://leetcode.com/mkhuzaima/
 * Github   : https://github.com/mkhuzaima
 * LinkedIn : https://www.linkedin.com/in/mkhuzaima/
 */

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);
            }
        }
        // not possible, since solution exists
        return null;
    }
}