Example: Radix Sort Implementation in C++

// Radix Sort Implementation
#include <iostream>
#include <vector>
#include <algorithm> // Required for std::max_element

// Function to get the maximum value from an array
int getMax(const std::vector<int>& arr) {
    int maxVal = arr[0];
    for (size_t i = 1; i < arr.size(); ++i) {
        if (arr[i] > maxVal) {
            maxVal = arr[i];
        }
    }
    return maxVal;
}

// A function to do counting sort of arr[] according to
// the digit represented by exp.
void countingSort(std::vector<int>& arr, int exp) {
    int n = arr.size();
    std::vector<int> output(n); // Output array
    std::vector<int> count(10, 0); // Count array for digits 0-9

    // Store count of occurrences in count[]
    for (int 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 (int i = 1; i < 10; ++i) {
        count[i] += count[i - 1];
    }

    // Build the output array
    // Iterate from right to left to ensure stability
    for (int 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 (int i = 0; i < n; ++i) {
        arr[i] = output[i];
    }
}

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

    // Do counting sort for every digit. Note that exp is 10^i
    // where i is current digit number
    for (int exp = 1; m / exp > 0; exp *= 10) {
        countingSort(arr, exp);
    }
}

int main() {
    // Step 1: Initialize an array of integers
    std::vector<int> arr = {170, 45, 75, 90, 802, 24, 2, 66};
    
    std::cout << "Original array: ";
    for (int x : arr) {
        std::cout << x << " ";
    }
    std::cout << std::endl;

    // Step 2: Call Radix Sort to sort the array
    radixSort(arr);

    // Step 3: Print the sorted array
    std::cout << "Sorted array: ";
    for (int x : arr) {
        std::cout << x << " ";
    }
    std::cout << std::endl;

    // Test with another array
    std::vector<int> arr2 = {329, 457, 657, 839, 436, 720, 355};
    std::cout << "\nOriginal array 2: ";
    for (int x : arr2) {
        std::cout << x << " ";
    }
    std::cout << std::endl;
    radixSort(arr2);
    std::cout << "Sorted array 2: ";
    for (int x : arr2) {
        std::cout << x << " ";
    }
    std::cout << std::endl;

    return 0;
}