finding the largest element in an array using functions

Question

This is the question I've tried to attempt "Given an array A[] of size n. The task is to find the largest element in it.

Input:

n = 5
A[] = {1, 8, 7, 56, 90}

Output:

90

Explanation:

The largest element of the given array is 90.
I'm unable to get the desired outcome, my output screen freezes. I think the problem is in passing by reference, please help me solve and understand my mistake

Here's my code:

#include <iostream>

using namespace std;

int largest(int* arr[], int* n) {
  int max = 0;
  for (int first = 0; first <* n; first++) {
    if (*arr[first] > max) {
      max = *arr[first];
    }

  }

  return max;
}

int main() {
  cout << "enter how many numbers you want in an array = ";
  int userinput;
  cin >> userinput;
  int* myarray=new int[userinput];
  for (int loop = 0; loop < userinput; loop++) {
    cin >> myarray[loop];
  }
  cout << "Your array = { ";
  for (int loop = 0; loop < userinput; loop++) {
    cout<< myarray[loop]<<" ";
  }
  cout << "}";
  cout << endl;
  cout<< "Largest number in the array = "<<largest(&myarray,&
                                                   userinput);
  return 0;
}

You don't need to pass anything either by reference or by pointer. — molbdnilo, Aug 13 '21 at 12:25
BTW, [do not define the `std`` namespace globaly](https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice). — Ghasem Ramezani, Aug 13 '21 at 17:00

score 1 · Answer 1 · answered Aug 13 '21 at 12:20

1

You should use the argument arr to read the array.
You should use = operator, not ==, to perform assignment.
You should add indentation to make your code easy to read.
Using fixed value for the initial value of max will make it produce wrong output when all of the elements of the array ls less than the initial value.

Fixed code:

int largest(int *arr[], int *n)
{
    if (*n <= 0) return 0;
    int max = (*arr)[0];
    for (int first = 0; first <* n; first++)
    {
        if ((*arr)[first] > max)
        {
            max = (*arr)[first];
        }

    }

    return max;
}

answered Aug 13 '21 at 12:20

MikeCAT

73,922
11
45
70

thank you so much for quick response ! it worked ! ive noticed if i dont add ( ) in the *arr, my output screen freezes, why is that? – codeplayer Aug 13 '21 at 12:30
@codeplayer Because `[]` operator has higher precedence than unary `*` operator and removing `()` will lead to out-of-range access of the "one-element array" whose element is `myarray`. – MikeCAT Aug 13 '21 at 12:37
Really try to use the std library containers (std::array, std::vector, std::list) instead of plain arrays. Code like this is more likely to contain bugs, like overshooting the boundaries of the array. And you can use the for(auto x : collection) syntax for safe enumeration over the elements in the collections. – Pepijn Kramer Aug 13 '21 at 12:40

score 1 · Answer 2 · answered Aug 13 '21 at 12:31

Most common problems already have a solution, in this case the standard library.

#include <algorithm>

std::array<int, 4> ar{ 1, 4, 42, 2 };
auto max_value = *std::max_element(ar.begin(), ar.end());

This will set max_value to 42. In your case you could also use a std::vector instead of an array and push_back any entries the user entered.

std::cout << "enter how many numbers you want in an array = ";
int userinput{0};
std::cin >> userinput;
std::vector<int> values;

for (int loop = 0; loop < userinput; loop++) {
    int new_value{ 0 };
    std::cin >> new_value;
    values.push_back(new_value);
}

std::cout << "Your array = { ";
for (const auto value : values)
{
    std::cout << value << " ";
}

std::cout << "}";
std::cout << std::endl;

auto max_value = *std::max_element(values.begin(), values.end());
std::cout << "Largest number in the array = " << max_value;

finding the largest element in an array using functions

Input:

Output:

Explanation:

2 Answers2