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 <iostream>      #include <ctime>         #include <algorithm>     #include <vector>         using namespace std;  int binarySearch(int first, int last, int search4, vector<int>& random);  int main() {     vector<int> 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<int>& random) {     do     {         int mid = (first + last) / 2;           if (search4 > random[mid])              first = mid + 1;           else if (search4 < random[mid])              last = mid - 1;          else             return mid;          } while (first <= last);       return -(first + 1); } 

Answer 1

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<int>& random);  vector<int> random(100); // ... found = binarySearch(first, last, search4, random); 

As a pointer:

int binarySearch(int first, int last, int search4, vector<int>* random);  vector<int> random(100); // ... found = binarySearch(first, last, search4, &random); 

Inside binarySearch, you will need to use . or -> to access the members of random correspondingly.

Issues with your current code

1. binarySearch expects a vector<int>*, but you pass in a vector<int> (missing a & before random)
2. You do not dereference the pointer inside binarySearch before using it (for example, random[mid] should be (*random)[mid]
3. You are missing using namespace std; after the <include>s
4. The values you assign to first and last are wrong (should be 0 and 99 instead of random[0] and random[99]