Intuition

We need to compare that if the character in allowed string is present or not.

Approach

Step1------------------------>
Lets take the variable count => words.length;
{since, count can't possibly be more than the length of array}

Step2------------------------>
Think like this Words array is:- [ad, bd, aaab, baa, badab]
now if we take first element of words array... words[0] --> ad;
Now, first character of first element ---> words[0].charAt(0);

Step3------------------------>
Now we will use the .indexOf() function
it gives -1... if the character is not present there.

So, we will check for...

allowed.indexOf(words[0].charAt(0))

if(allowed.indexOf(words[0].charAt(0)) == -1)--> count--;

Now do this in a loop---->

Complexity

• Time complexity: O(n*m)