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;
}
}
