TwoSum

import java.util.Map;
import java.util.HashMap;
import java.util.List;
import java.util.ArrayList;
class Main {
    public static void main(String[] args) {
        System.out.println("Hello World!");
        int[] arr={2,3,4,6,5};
        int target=9;
        List<int[]> result=twoSum(arr,target);
        for(int[] pair:result){
        System.out.println(pair[0]+","+pair[1]);
        }
    }
    
    public static  List<int[]> twoSum(int[] arr, int target){
        Map<Integer, Integer> arrMap=new HashMap<>();
        int complement;
        List<int[]> result=new ArrayList<>();
        for(int i=0;i<arr.length;i++){
            complement=target-arr[i];
            if(arrMap.containsKey(complement)){
               // return new int[] {arrMap.get(complement),i};
               result.add(new int[] { arrMap.get(complement), i });

            }
            arrMap.put(arr[i],i);
        }
        //throw new IllegalArgumentException("Not found");
        return result;
    }
}