counting sort impolementation not from memory

counting_sort.cpp

#include <iostream>
#include <bits/stdc++.h>

int a[] = {9,3,1,4,5,7,7,2,2};

void counting_sort(int a[], int n) {
  int radix = *std::max_element(a, a+n);
  int c[radix+1] = {};
  int b[n] = {};

  for (int i=0; i<n; i++) {
    c[a[i]]++;
  }
  for (int i=1; i<=radix; i++) {
    c[i] = c[i-1] + c[i];
  }
  for (int i=n-1; i>-1; i--) {
    int m = a[i];
    c[m]--;
    b[c[m]] = a[i];
  }
  for (int i=0; i<n; i++) {
    a[i] = b[i];
  }
}

int main() {

  int n = sizeof(a)/sizeof(a[0]);

  counting_sort(a, n);
  for (int i = 0; i<n; i++) {
    std::cout << a[i] << " ";
  }
  std::cout << "\n";

  return 1;
}