import java.util.*;
import java.lang.*;
import java.io.*;

// The main method must be in a class named "Main".
class Main {
    private static int[] twoSum(int[] nums, int target) {
        HashMap<Integer, Integer> map = new HashMap<>();

        for (int i = 0; i < nums.length; i++) {
            int diff = target - nums[i];
            if (map.containsKey(diff)) {
                return new int[] {map.get(diff), i};
            }
            map.put(nums[i], i);
        }
        return null;
    }
    
    public static void main(String[] args) {
        System.out.println("Two Sum - Leetcode 1 - HashMap");
        int[] nums = new int[] {0, 1, 2, 3, 4, 5};
        System.out.println(Arrays.toString(nums));
        for (int i = 0; i < 12; i++) {
            System.out.println(i + " : " + Arrays.toString(twoSum(nums, i)));
        }
        
    }
}