replacing a vector elemnts from another vector of the same size

Hello

Im trying to replace some values in one vector to values from another vector in the same location

let says this is my vector:

5
3
8
2
3

and i have this vector

99
0
23
0
0

I want to replace zeros in the second vector to be like this

99
3
23
2
3

Are there any effiecient way to do that

Many thanks

Answer 1

[Walter Roberson]

mask = second_vector == 0;
second_vector(mask) = first_vector(mask);

[A Aln]

Thank you !!