448_Find All Numbers Disappeared in an Array

/*
448_Find All Numbers Disappeared in an Array
Runtime: 3 ms, faster than 100.00% of Java online submissions for Find All Numbers Disappeared in an Array.
Memory Usage: 48.6 MB, less than 68.01% of Java online submissions for Find All Numbers Disappeared in an Array.*/


class Solution {
    public List<Integer> findDisappearedNumbers(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++)
            arr[nums[i]]=true;
        
        
        
        
       for(int i=1;i<=nums.length;i++)
       {
           if(arr[i]==false)
               arr1.add(i);
       }
        
        return arr1;
    }
}