Parallel Count Sort – GeeksforGeeks

#include <iostream>

#include <omp.h>

#include <vector>

using namespace std;

int getMax(vector<int> arr, int n)

{

    int mx = arr[0];

    for (int i = 1; i < n; i++)

        if (arr[i] > mx)

            mx = arr[i];

    return mx;

}

void countSort(vector<int>& arr, int n, int exp)

{

    int output[n];

    int i, count[10] = { 0 };

    for (i = 0; i < n; i++)

        count[(arr[i] / exp) % 10]++;

    for (i = 1; i < 10; i++)

        count[i] += count[i - 1];

    for (i = n - 1; i >= 0; i--) {

        output[count[(arr[i] / exp) % 10] - 1] = arr[i];

        count[(arr[i] / exp) % 10]--;

    }

    for (i = 0; i < n; i++)

        arr[i] = output[i];

}

void parallelCountSort(vector<int>& arr, int n)

{

    int m = getMax(arr, n);

    for (int exp = 1; m / exp > 0; exp *= 10) {

        for (int i = 0; i < n; i++)

            countSort(arr, n, exp);

    }

}

int main()

{

    vector<int> arr = { 170, 45, 75, 90, 802, 24, 2, 66 };

    int n = arr.size();

    cout << "Array before sorting: \n";

    for (int i = 0; i < n; i++) {

        cout << arr[i] << " ";

    }

    cout << "\n";

    parallelCountSort(arr, n);

    cout << "Array after sorting: \n";

    for (int i = 0; i < n; i++) {

        cout << arr[i] << " ";

    }

    return 0;

}