Example: Radix Sort Implementation in C

// Radix Sort Implementation
#include <stdio.h>
#include <stdlib.h> // For malloc, free, abs
#include <limits.h> // For INT_MIN

// Function to get the maximum value in an array
int getMax(int arr[], int n) {
    int max = arr[0];
    for (int i = 1; i < n; i++) {
        if (arr[i] > max) {
            max = arr[i];
        }
    }
    return max;
}

// A function to do counting sort of arr[] according to
// the digit represented by exp.
void countSort(int arr[], int n, int exp) {
    int output[n]; // output array
    int i, count[10] = {0}; // Count array for digits 0-9

    // Store count of occurrences in count[]
    for (i = 0; i < n; i++) {
        count[(arr[i] / exp) % 10]++;
    }

    // Change count[i] so that count[i] now contains actual
    // position of this digit in output[]
    for (i = 1; i < 10; i++) {
        count[i] += count[i - 1];
    }

    // Build the output array
    // Iterate from right to left to ensure stability
    for (i = n - 1; i >= 0; i--) {
        output[count[(arr[i] / exp) % 10] - 1] = arr[i];
        count[(arr[i] / exp) % 10]--;
    }

    // Copy the output array to arr[], so that arr[] now
    // contains sorted numbers according to current digit
    for (i = 0; i < n; i++) {
        arr[i] = output[i];
    }
}

// The main function to that sorts arr[] of size n using Radix Sort
void radixSort(int arr[], int n) {
    // Step 1: Find the maximum number to know number of digits
    int m = getMax(arr, n);

    // Step 2: Do counting sort for every digit. Note that instead
    // of passing digit number, exp is passed. exp is 10^i where i is current
    // digit number
    for (int exp = 1; m / exp > 0; exp *= 10) {
        countSort(arr, n, exp);
    }
}

// Function to print an array
void printArray(int arr[], int n) {
    for (int i = 0; i < n; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}

int main() {
    // Step 1: Define an array of integers
    int arr[] = {170, 45, 75, 90, 802, 24, 2, 66};
    int n = sizeof(arr) / sizeof(arr[0]);

    printf("Original array: ");
    printArray(arr, n);

    // Step 2: Apply Radix Sort
    radixSort(arr, n);

    printf("Sorted array: ");
    printArray(arr, n);

    return 0;
}