How to find factors of each number in an array - c++

Question

I have an array of numbers input by the user, the program then sorts it in ascending order. I just need to find a way to get the factors of each number in the array and have it be printed out
#include "stdafx.h"
#include <iostream>
#include <limits>
#define MAX 200
using namespace std;
int arr[MAX];
int n, i, j, k;
int temp;
int main()
{
//array declaration
int arr[MAX];
int n, i, j;
int temp;
//read total number of elements to read
cout << "Enter total number of numbers to read: ";
cin >> n;
//check bound
if (n<0 || n>MAX)
{
cout << "Input valid range!!!" << endl;
return -1;
}
//read n elements
for (i = 0; i < n; i++)
{
cout << "Enter element [" << i + 1 << "] ";
cin >> arr[i];
cout << endl;
}
//print input elements
cout << "Unsorted Array elements:" << endl;
for (i = 0; i < n; i++)
cout << arr[i] << "\t";
cout << endl;
//sorting - ASCENDING ORDER
for (i = 0; i<n; i++)
{
for (j = i + 1; j < n; j++)
{
if (arr[i]>arr[j])
{
temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
}
//print sorted array elements
cout << endl;
cout << "Sorted (Ascending Order) Array elements:" << endl;
for (i = 0; i < n; i++)
cout << arr[i] << "\t";
cout << endl <<endl;
//trying to find factors
cout << "Factors of " << arr[i] << " are: " << endl;
for (k = 1; k <= arr[i]; ++i)
{
if (arr[i] % k == 0)
cout << k << endl;
}
system ("pause")
return 0;
}
I want it to print each number from the array with
"The factors of (number) are ...'
"The factors of (next number) are ..."
and so on

Answer 1

The final for-loop should be loop with k and you forgot to increment k.
You should also write i-loop:
//trying to find factors
for (i = 0; i < n; i++)
{
cout << "Factors of " << arr[i] << " are: " << endl;
for (k = 1; k <= arr[i]; ++k)
{
if (arr[i] % k == 0)
cout << k << endl;
}
}
In addition, as pointed out by #LocTran, the upper bound of outer loop should be n-1.
Alternatively, you can easily sort arr using std::sort as follows:
std::sort(arr, arr+n);
Then your code would well work for you:
Live Demo

Answer 2

There are some issues with your source code.
1> Sorting problem with for outer loop
//sorting - ASCENDING ORDER
for (i = 0; i < (n-1); i++)
{
for (j = i + 1; j < n; j++)
{
if (arr[i] > arr[j])
{
temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
}
The upper bound of outer loop should be (n-1), not n as following but maybe you're lucky you won't see the problem when n < MAX. In case of n == MAX you will see the problem
//sorting - ASCENDING ORDER
//for (i = 0; i < n; i++)
for (i = 0; i < (n-1); i++)
{
for (j = i + 1; j < n; j++)
{
if (arr[i] > arr[j])
{
temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
}
2> The print functionality for entire array, you should add the outer loop for index of your array, and change the i++ by k++ in your loop as well
//trying to find factors
cout << "Factors of " << arr[i] << " are: " << endl;
for (k = 1; k <= arr[i]; ++i)
{
if (arr[i] % k == 0)
cout << k << endl;
}
should be replaced by
//trying to find factors
for (i = 0; i < n; i++)
{
cout << "Factors of " << arr[i] << " are: " << endl;
//for (k = 1; k <= arr[i]; ++i)
for (k = 1; k <= arr[i]; ++k)
{
if (arr[i] % k == 0)
cout << k << endl;
}
}
Here is my solution based on modified source code
#include <iostream>
#include <limits>
#define MAX 200
using namespace std;
int arr[MAX];
int n, i, j, k;
int temp;
int main()
{
//array declaration
int arr[MAX];
int n, i, j;
int temp;
//read total number of elements to read
cout << "Enter total number of numbers to read: ";
cin >> n;
//check bound
//if (n<0 || n>MAX)
if (n<0 || n>MAX)
{
cout << "Input valid range!!!" << endl;
return -1;
}
//read n elements
for (i = 0; i < n; i++)
{
cout << "Enter element [" << i + 1 << "] ";
cin >> arr[i];
cout << endl;
}
//print input elements
cout << "Unsorted Array elements:" << endl;
for (i = 0; i < n; i++)
cout << arr[i] << "\t";
cout << endl;
//sorting - ASCENDING ORDER
//for (i = 0; i < n; i++)
for (i = 0; i < (n-1); i++)
{
for (j = i + 1; j < n; j++)
{
if (arr[i] > arr[j])
{
temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
}
//print sorted array elements
cout << endl;
cout << "Sorted (Ascending Order) Array elements:" << endl;
for (i = 0; i < n; i++)
cout << arr[i] << "\t";
cout << endl << endl;
//trying to find factors
for (i = 0; i < n; i++)
{
cout << "Factors of " << arr[i] << " are: " << endl;
//for (k = 1; k <= arr[i]; ++i)
for (k = 1; k <= arr[i]; ++k)
{
if (arr[i] % k == 0)
cout << k << endl;
}
}
return 0;
}