radix_sort_2.c

//sorting of array list using Radix sort
#include <stdio.h>

#define range 10  // Range for integers is 10 as digits range from 0-9

// Utility function to get the maximum value in ar[]
int MAX(int ar[], int size){
    int i, max = ar[0];
    for(i = 0; i<size; i++){
        if(ar[i]>max)
            max = ar[i];
    }
    return max;
}

// Counting sort according to the digit represented by place
void countSort(int arr[],int n,int place)
{
        int i,freq[range]={0};         
        int output[n];
    
        // Store count of occurences in freq[]
        for(i=0;i<n;i++)
                freq[(arr[i]/place)%range]++;
    
        // Change freq[i] so that it contains the actual position of the digit in output[]
        for(i=1;i<range;i++)
                freq[i]+=freq[i-1];
    
        // Build the output array
        for(i=n-1;i>=0;i--)
        {
                output[freq[(arr[i]/place)%range]-1]=arr[i];
                freq[(arr[i]/place)%range]--;
        }
        
        // Copy the output array to arr[], so it contains numbers according to the current digit
        for(i=0;i<n;i++)
                arr[i]=output[i];
}

/*This is where the sorting of the array takes place
 arr[] --- Array to be sorted
 n --- Array Size
 max --- Maximum element in Array
 */
void radixsort(int arr[],int n,int max)            //max is the maximum element in the array
{
        int mul=1;
        while(max)
        {
                countsort(arr,n,mul);
                mul*=10;
                max/=10;
        }
}

int main(int argc, const char * argv[]){
    int n;
    printf("Enter size of array:\n");
    scanf("%d", &n); // E.g. 8
    
    printf("Enter the elements of the array\n");
    int i;
    int arr[n];
    for(i = 0; i < n; i++){
        scanf("%d", &arr[i] );
    }
    
    printf("Original array: ");
    display(arr, n);                   // Original array : 10 11 9 8 4 7 3 8
    
    int max;
    max = MAX(arr,n);
    
    radixsort(arr, n, max);
    
    printf("Sorted array: ");
    display(arr, n);                // Sorted array : 3 4 7 8 8 9 10 11
    
    return 0;


}