Recusrsion(Count Binary Strings)

#1

i did not understood the approach for the question and can’t able to understand the logic which was explained.Can you please help me in this?

#2

in video it is clearly explain the approach
which thing you didn’t get exactly

the approach is

to make string of size N
we have two option to put char at str[n-1]
// Option 1
we can put ‘0’ if so then at str[n-2] we can put anything
hence we just call for f(n-1)

// Option 2
we can also put ‘1’ if so then at str[n-2] we have to put ‘0’
otherwise there will be two consecutive 1
so we call for f(n-2)

now we have recurence relation
f(N)=f(N-1)+f(N-2)

just implement this
this is same as fibo series