442_Find All Duplicates in an Array

/*442_Find All Duplicates in an Array
Runtime: 3 ms, faster than 100.00% of Java online submissions for Find All Duplicates in an Array.
Memory Usage: 48 MB, less than 95.97% of Java online submissions for Find All Duplicates in an Array.*/


class Solution {
    public List<Integer> findDuplicates(int[] nums) {
        
        ArrayList<Integer> arr1=new ArrayList<>();
        boolean[] arr= new boolean[nums.length+1] ;
        
    for(int i=0;i<=nums.length;i++)
        arr[i]=false;
       
      
         
            
    for(int i=0;i<nums.length;i++)
    {        if(arr[nums[i]]==true)
                arr1.add(nums[i]);
            arr[nums[i]]=true;
    }   
        
        
          // for(int i=0;i<nums.length;i++)
          //    System.out.println(arr[i]);
        
     
        
        return arr1;
        
    }
}