finding the most repeated elements in an array with length n - c++

Question

const int N=10;
int main()
{
int arr[N]={4,4,6,4,6,6,7,9,9,9};
for (int i = 0; i < N; i++)
for (int j=i+1; j<N; j++)
{
if (arr[i]==arr[j])
cout << arr[i];
}
return 0;
}
This gives all the repeated elements (meaning it will give 444,666,999). My problem is that I want the output to be just 4,6,9 and not that 4 was repeated three times. Obviously I gave my global constant a value of 10 but how can i do this for an "n" (unknown) number. Thanks.

Answer 1

At the beginning sort array
sort(arr, arr + n);
Then iterate and find the count of the most repeated element, you can do that like this :
int maxCnt = 0;
int curCnt = 1;
for (int i = 1; i < n; i++) {
if (arr[i] == arr[i - 1]) curCnt++;
else
{
maxCnt = max(maxCnt, curCnt);
curCnt = 1;
}
}
maxCnt = max(maxCnt, curCnt);
then iterate again accumulating curCnt and when curCnt == maxCnt output number
curCnt = 1;
for (int i = 1; i < n; i++) {
if (curCnt == maxCnt) cout << arr[i - 1] << ' ';
if (arr[i] == arr[i - 1]) {
curCnt++;
}
else curCnt = 1;
}
if (curCnt == maxCnt) cout << arr[n - 1] << endl;
This solution will output the most repeated numbers only once.

Answer 2

Use "range based for loop" for unknown array size (N).
Use std::map to calculate the count for each element.
Here is the code:
#include <map>
#include <iostream>
using namespace std;
int main()
{
const int arr[]{ 4,4,6,4,6,6,7,9,9,9 };
// Get count for each element.
map<int, int> elementCount;
for (const auto& e : arr)
{
elementCount[e] += 1;
}
// Get the highest count.
int highestCount = 0;
for (const auto& e : elementCount)
{
cout << e.first << " " << e.second << endl;
if (e.second > highestCount)
{
highestCount = e.second;
}
}
// Get the elements with the hightest count.
cout << endl << "Elements with the hightest count:" << endl;
for (const auto& e : elementCount)
{
if (e.second == highestCount)
{
cout << e.first << " ";
}
}
cout << endl;
return 0;
}