## Topics Covered

• Algorithm for radix sort
• C program to implement radix sort
• C++ program to implement radix sort

## Algorithm for radix sort

``````1. Take input in the array.
2. Get the maximum element.
3. Run the countsort() till (m/exp) > 0.
4. Sort the elements on the basis of the element at (exp)th place.
5. Assign the sorted elements back to array[].
6. Check the condition in step 3.
7. If false, print the sorted output array.
8. Exit the program.``````

## C program to implement radix sort

``````
#include <stdio.h>
#include <conio.h>
// Function applied to obtain the largest element from the array
int getMax(int array[], int n) {
int max = array[0];
for (int i = 1; i < n; i++)
if (array[i] > max)
max = array[i];
return max;
}
// Apply counting sort to sort the elements on the basis of specific positions
void countingsort(int array[], int size, int place) {
int output[size + 1];
int max = (array[0] / place) % 10;
for (int i = 1; i < size; i++) {
if (((array[i] / place) % 10) > max)
max = array[i];
}
int count[max + 1];
for (int i = 0; i < max; ++i)
count[i] = 0;
// Calculate the total count of elements
for (int i = 0; i < size; i++)
count[(array[i] / place) % 10]++;
// Calculate cummulative counts
for (int i = 1; i < 10; i++)
count[i] += count[i - 1];
// Place all the elements in the sorted order
for (int i = size - 1; i >= 0; i--) {
output[count[(array[i] / place) % 10] - 1] = array[i];
count[(array[i] / place) % 10]--;
}
for (int i = 0; i < size; i++)
array[i] = output[i];
}
// main function to implement radix sort
void radixsort(int array[], int size) {
// Get the maximum element among them
int max = getMax(array, size);
// Apply counting sort to sort elements based on place value
for (int place = 1; max / place > 0; place *= 10)
countingsort(array, size, place);
}
// Print an array
void printArray(int array[], int size) {
for (int i = 0; i < size; ++i) {
printf("%d  ", array[i]);
}
printf("\n");
}
// Driver code
int main() {
int array[] = {121, 432, 564, 23, 1, 45, 788};
int n = sizeof(array) / sizeof(array[0]);
printf("The final sorted array is : \n");
printArray(array, n);
}``````

## C++ program to implement radix sort

``````#include <iostream>
using namespace std;

// Get maximum value from the array
int getMax(int array[], int n)
{
int maximum = array[0];
for (int i = 1; i < n; i++)
if (array[i] > maximum)
maximum = array[i];
return maximum;
}

// Apply count sort for arr[].
void countSort(int array[], int n, int exp)
{
// Count[i] array counting the number of array values having that 'i' digit at their (exp)th place.
int output[n], i, count[10] = {0};

// Count the number of times each digit occurred at (exp)th place in every input.
for (i = 0; i < n; i++)
count[(array[i] / exp) % 10]++;

// Calculating their cumulative count
for (i = 1; i < 10; i++)
count[i] += count[i-1];

// Inserting values according to the digit '(arr[i] / exp) % 10' fetched into count[(arr[i] / exp) % 10].
for (i = n - 1; i >= 0; i--)
{
output[count[(array[i] / exp) % 10] - 1] = array[i];
count[(array[i] / exp) % 10]--;
}

// Assigning the result to the array pointer of main() function.
for (i = 0; i < n; i++)
array[i] = output[i];
}

// Sorting the array[] of size n using Radix Sort.
void radixsort(int array[], int n)
{
int exp, m;
m = getMax(array, n);

// Calling countSort() for digit at (exp)th place in every input.
for (exp = 1; m/exp > 0; exp *= 10)
countSort(array, n, exp);
}

int main()
{
int n, i;
cout<<"\nEnter the size of the array to be sorted: ";
cin>>n;
//apply loop for taking the elements in the array
int array[n];
for(i = 0; i < n; i++)
{
cout<<"Enter element "<<i+1<<": ";
cin>>array[i];
}

// Printing the final sorted data
cout<<"Final sorted array is : "<<endl;
for (i = 0; i < n; i++)
cout<<" "<<array[i];
return 0;
}``````
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