What is a counting sort algorithm?

#include<iostream>
#include<algorithm>
using namespace std;
// function for printing an array.
void printArr(int *array, int size) {
   for(int i = 0; i < size; i++)
      cout << array[i] << " ";
   cout << endl;
}
// function for calculating maximum element.
int findMax(int array[], int size) {
   int max = array[0];
   for(int i = 1; i < size; i++) {
      if(array[i] > max)
         max = array[i];
   }
   return max; 
}
// function for the count sort algorithm
void countSort(int *array, int size) {
   int output[size];
   
   int max = findMax(array, size);
   int count[max+1]; 
   for(int i = 0; i <= max; i++)
      count[i] = 0;  //initialize frequencies array to all zero
   for(int i = 0; i < size; i++)
      count[array[i]]++;   //fill the array with the count of each number
   for(int i = 1; i <= max; i++)
      count[i] += count[i-1]; //find cumulative frequency
   for(int i = size - 1 ; i>=0; i--) {
      output[count[array[i]]-1] = array[i];
      count[array[i]] -= 1;   //decrease count for same numbers
   }
   for(int i = 0; i < size; i++) {
      array[i] = output[i];   //store output array to main array
   }
}
int main() {
   int arr[] = {1, 5, 9, 8, 1, 3};
   int n = 6;
   cout << "Array before Sorting: ";
   printArr(arr, n);
   countSort(arr, n);
   cout << "Array after Sorting: ";
   printArr(arr, n);
}

#include<iostream>
#include<algorithm>
using namespace std;
// function for printing an array.
void printArr(int *array, int size) {
   for(int i = 0; i<size; i++)
      cout << array[i] << " ";
   cout << endl;
}
// function for calculating maximum element.
int findMax(int array[], int size) {
   int max = array[0];
   for(int i = 1; i < size; i++) {
      if(array[i] > max)
         max = array[i];
   }
   return max; 
}
// function for calculating minimum element.
int findMin(int array[], int size) {
   int min = array[0];
   for(int i = 1; i < size; i++) {
      if(array[i] < min)
         min = array[i];
   }
   return min; 
}
// function for the count sort algorithm
void countSort(int *array, int size) {
   int output[size];
   int min = findMin(array, size); 
   for(int i = 0; i < size; i++)
      array[i]-=min; // subtracting minimum value from the array to start range from 0
   int max = findMax(array, size);
   int count[max+1]; 
   for(int i = 0; i<=max; i++)
      count[i] = 0;  //initialize frequencies array to all zero
   for(int i = 0; i < size; i++)
      count[array[i]]++;   //fill the array with the count of each number
   for(int i = 1; i<=max; i++)
      count[i] += count[i-1]; //find cumulative frequency
   for(int i = size - 1 ; i>=0; i--) {
      output[count[array[i]]-1] = array[i];
      count[array[i]] -= 1;   //decrease count for same numbers
   }
   for(int i = 0; i < size; i++) {
      array[i] = output[i] + min; //store output array to main array with the actual values
   }
}
int main() {
   int arr[] = {1, 5, 9, 8, -1, -3};
   int n = 6;
   cout << "Array before Sorting: ";
   printArr(arr, n);
   countSort(arr, n);
   cout << "Array after Sorting: ";
   printArr(arr, n);
}