Count number of binary strings

#1

I have tried this question using recursion but I am getting TLE. Can I get some hint to optimize my code?

#2

Use DP to avoid tle.
Bottom is easy to implement.

#3

Can it be solved using bit manipulation?

#4

I am not able to think this problem approach using DP. Can you please help me.

#5

for (int i = 1; i < n; i++)
{
a[i] = a[i-1] + b[i-1];
b[i] = a[i-1];
}

In array a , we store if last element was 0.
In array b , we store if last element was 1.

Just return a[n-1]+b[n-1]

#6

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