How to pass a vector to a function

Question

I m trying to send a vector as an argument to a function and i can t figure out how to make it work  Tried a bunch of different ways but they all give different error messages  I only include part of the code  since it s only this part that doesn t work   the vector  random  is filled with random  but sorted  values between 0 and 200   Updated the code    include  lt iostream gt        include  lt ctime gt           include  lt algorithm gt       include  lt vector gt          using namespace std   int binarySearch int first  int last  int search4  vector lt int gt  amp  random    int main         vector lt int gt  random 100        int search4  found      int first   0      int last   99       found   binarySearch first  last  search4  random        system  pause            return 0            int binarySearch int first  int last  int search4  vector lt int gt  amp  random        do               int mid    first   last    2            if  search4  gt  random mid                first   mid   1            else if  search4  lt  random mid                last   mid - 1           else             return mid             while  first  lt   last         return - first   1

User · Accepted Answer

It depends on if you want to pass the vector as a reference or as a pointer  I am disregarding the option of passing it by value as clearly undesirable    As a reference   int binarySearch int first  int last  int search4  vector lt int gt  amp  random    vector lt int gt  random 100          found   binarySearch first  last  search4  random     As a pointer   int binarySearch int first  int last  int search4  vector lt int gt   random    vector lt int gt  random 100          found   binarySearch first  last  search4   amp random     Inside binarySearch  you will need to use   or - gt  to access the members of random correspondingly   Issues with your current code   binarySearch expects a vector lt int gt    but you pass in a vector lt int gt   missing a  amp  before random  You do not dereference the pointer inside binarySearch before using it  for example  random mid  should be   random  mid  You are missing using namespace std  after the  lt include gt s The values you assign to first and last are wrong  should be 0 and 99 instead of random 0  and random 99

User · Answer

If you use random instead of   random your code not give any error

User · Answer

Anytime you re tempted to pass a collection  or pointer or reference to one  to a function  ask yourself whether you couldn t pass a couple of iterators instead  Chances are that by doing so  you ll make your function more versatile  e g   make it trivial to work with data in another type of container when if needed    In this case  of course  there s not much point since the standard library already has perfectly good binary searching  but when if you write something that s not already there  being able to use it on different types of containers is often quite handy

User · Answer

found   binarySearch first  last  search4   amp random     Notice the  amp

User · Answer

You ll have to pass the pointer to the vector  not the vector itself  Note the additional   amp   here   found   binarySearch first  last  search4   amp random

User · Answer

You re using the argument as a reference but actually it s a pointer  Change vector lt int gt   to vector lt int gt  amp   And you should really set search4 to something before using it

User · Answer

You re passing in a pointer  random but you re using it like a reference  amp random  The pointer  what you have  says  This is the address in memory that contains the address of random   The reference says  This is the address of random

[c++] How to pass a vector to a function?

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