Passing the vector as a parameter

#1

when we are passing the vector as a parameter in the factorize function, why are we passing it by reference by using &

#2

also is there a possibility to pass the function of the prime sieve itself as a parameter in the factorize function as we have done earlier when we passed the compare function

#3

@vector.9974, we are passing by reference because passing by value is time inefficient , means if you pass a vector by value then it will take o(n) time to make a copy at every function call which is quite inefficient , this is why we pass vector by reference .

Let me show you by an example how,

So you have the given function as :-

int sum=0;`

void calcSum(vector<int> v,int i){  // call by value
    if(i==v.size()){
        return ;
    }
    sum+=v[i];
    calcSum(v,i+1);
    return ;
}

you might think that the complexity of function is o(n) . but wait…
you will notice that here function here is called by value
so every time you call the function then our original vector will be copied by the function and u know that copying a vector take O(n) so calling our function n times with subsequent copies will give us over all time complexity as O(n^2)
have the given function been like

int sum=0;

void calcSum(vector<int> &v,int i){ // call by reference 
    if(i==v.size()){
        return ;
    }
    sum+=v[i];
    calcSum(v,i+1);
    return ;
}

the time complexity would have been O(n), since reference does’nt require copying whole vector

In case of any doubt feel free to ask :slight_smile:
If you got your answer mark the doubt as RESOLVED

#4

yes you can pass the seive vector as a parameter

#5

pls share the syntax on how to pass the sieve vector as a parameter in the factorize function

#6

the syntax would be simple , you just have to make the seive using vector
say, vector seive;
and pass it to any function you are using by reference
eg:-

int fun(vector&seive){
…
}

#7

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