Comparing two Arrays

[Terribad13]

My job is to compare two Arrays (Array A, Array B) and set another Array (Array C) to elements of the other two arrays in descending order.

void setBigger(double bigger[], const double a[], const double b[], unsigned els) {
	double big = 0;
	cout << "{";
	for (unsigned pos = 0; pos < els; pos++) {
		double big = 0;
		for (unsigned posA = 0; posA < els; posA++) {
			if (a[posA] > big || b[posA] > big)
				if (a[posA] != big && b[posA] != big)
				big = max(b[posA], a[posA]);
		}
		bigger[pos] = big;
		cout << bigger[pos];
		if (pos >= 0 && pos < els-1)
			cout << ", ";
	}
	cout << "}";
}

This is what I have done so far. My issue is that it is setting all parts of Array C to the largest number rather than excluding that number and moving on. Any suggestions?

a[] is set to { 1, 2, 3, 4, 5, 6, 7 }
b[] is set to {10, 8, 6, 4, 2, 0, -2 }

All help is appreciated.

[Moschops]

and set another Array (Array C) to elements of the other two arrays in descending order.

This being C++, there is a lot the language provides. std::copy and std::sort from including algorithm, and std::greater from including functional.

Assuming that the arrays are all ready to go and the right sizes:

 std::copy ( a, a+els, bigger );
 std::copy ( b, b+els, bigger+els );
 std::sort(bigger, bigger+els*2, std::greater<int>());

[Thomas1965]

You could merge the arrays A + B into C and sort C.
Example:

#include <iostream>
#include <algorithm>
#include <functional>

using namespace std;

int main()
{
  const int NUM_ELEMS = 7;
  int a[NUM_ELEMS] = { 1, 2, 3, 4, 5, 6, 7 };
  int b[NUM_ELEMS] = {10, 8, 6, 4, 2, 0, -2 };
  int c[NUM_ELEMS * 2] = {0};
  
  for (int i = 0; i < NUM_ELEMS; i++)
  {
    c[i] = a[i];
  }
  for (int i = NUM_ELEMS, j=0; i < NUM_ELEMS * 2; i++, j++)
  {
    c[i] = b[j];
  } 
  cout <<"\nArray c unsorted: ";
  for (int i = 0; i < NUM_ELEMS * 2; i++)
  {
    cout << c[i] << " ";
  } 
  cout << "\n\n";
  std::sort(c, c + NUM_ELEMS * 2, greater<int>());

  cout <<"\nArray c sorted: ";
  for (int i = 0; i < NUM_ELEMS * 2; i++)
  {
    cout << c[i] << " ";
  } 
  cout << "\n\n";
  system("pause");
  return 0;
}

[riteshmalav]

well it depends if the given array are not sorted then you can use the approach given by Thomas1965 : merge the arrays and sort the merged array ...... complexity : O(n*long(n))

If yes then compare element by element and keep adding elements to the new array that way you will be able the solve the problem in O(n)

[dhayden]

First, recognize that if arrays a and b have els elements each, then array bigger will have 2*els elements.

What you're describing is called "merge sort" you solve it recursively.

[Terribad13]

I should have mentioned that array C also needs to be 7 elements long. This is why I am having so much troubles with this.

[Thomas1965]

array C also needs to be 7 elements long

This is not possible. If A and B have both 7 elements then combinded they will have 14 elements.