Returning an array from a function with arguments in c++

Question

I am trying to return an array from a local function to the main function but every time it shows a compilation error of

invalid conversion from ‘int’ to ‘int*’ [-f permissive]

#include <bits/stdc++.h>

using namespace std;

int* GCDstrings(int a,int b,int *F)
{
    int i;
    if(a%b==0)
    {
        F[0]=1;

        for(i=1;i<a;i++)
            F[i]=0;
    }

    return F;
}

int main()
{
    int T;
    cin>>T;

    while(T--)
    {
        int x,y;
        cin>>x>>y;

        int f[x];
        int* p;
        p=GCDstrings(x,y,f[x]);

        for(int i=0;i<=x;i++)
            cout<<*(p+i);
    }

    return 0;
}

What is the mistake I am doing here?

VLA is just a compiler extension and not supported by C++ standard. And why not use std::vector? — Hiroki
– Hiroki, Commented Jan 27, 2019 at 7:51
for(int i=0;i<=x;i++) will access the one past the end pointer... — Aconcagua
– Aconcagua, Commented Jan 27, 2019 at 8:01

anand_v.singh · Accepted Answer · 2019-01-27 07:46:16Z

3

You error lies in this part of your code

int f[x];
int* p; 
p=GCDstrings(x,y,f[x]);

You are trying to create a dynamic array and then pass it to the function.

When you pass an array you should only pass the location to its first value.

You can either do

p=GCDstrings(x,y,f);

during your function call.

Or you can go with,

p=GCDstrings(x,y,&f[0]);

For more information, check out this link https://www.programiz.com/cpp-programming/passing-arrays-function.

Also you might want to look into dynamic memory allocation for future, however it looks like you are beginning so allocating an array of length x like this is okay, but do check that out later. https://www.geeksforgeeks.org/new-and-delete-operators-in-cpp-for-dynamic-memory/

If any more problems, comment and we will see,

answered Jan 27, 2019 at 7:46

anand_v.singh

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