Radix sort is non-comparative sorting algorithm. This sorting algorithm works on the integer keys by grouping digits which share the same position and value. The radix is the base of a number system. As we know that in decimal system the radix or base is 10. So for sorting some decimal numbers, we need 10 positional box to store numbers.
The complexity of Radix Sort Technique
Time Complexity: O(nk)
Space Complexity: O(n+k)
Input − The unsorted list: 802 630 20 745 52 300 612 932 78 187 Output − Data after Sorting: 20 52 78 187 300 612 630 745 802 932
Algorithm
radixSort(array, size, maxDigit)
Input: An array of data, and the total number in the array, digit count of max number.
Output: Sorted array.
Begin define 10 lists as pocket for i := 0 to max -1 do m = 10i+1 p := 10i for j := 0 to n-1 do temp := array[j] mod m index := temp / p pocket[index].append(array[j]) done count := 0 for j := 0 to radix do while pocket[j] is not empty array[count] := get first node of pocket[j] and delete it count := count +1 done done End
Example Code
#include<iostream>
#include<list>
#include<cmath>
using namespace std;
void display(int *array, int size) {
for(int i = 0; i<size; i++)
cout << array[i] << " ";
cout << endl;
}
void radixSort(int *arr, int n, int max) {
int i, j, m, p = 1, index, temp, count = 0;
list<int> pocket[10]; //radix of decimal number is 10
for(i = 0; i< max; i++) {
m = pow(10, i+1);
p = pow(10, i);
for(j = 0; j<n; j++) {
temp = arr[j]%m;
index = temp/p; //find index for pocket array
pocket[index].push_back(arr[j]);
}
count = 0;
for(j = 0; j<10; j++) {
//delete from linked lists and store to array
while(!pocket[j].empty()) {
arr[count] = *(pocket[j].begin());
pocket[j].erase(pocket[j].begin());
count++;
}
}
}
}
int main() {
int n, max;
cout << "Enter the number of elements: ";
cin >> n;
cout << "Enter the maximum digit of elements: ";
cin >> max;
int arr[n]; //create an array with given number of elements
cout << "Enter elements:" << endl;
for(int i = 0; i<n; i++) {
cin >> arr[i];
}
cout << "Data before Sorting: ";
display(arr, n);
radixSort(arr, n, max);
cout << "Data after Sorting: ";
display(arr, n);
}Output
Enter the number of elements: 10 Enter the maximum digit of elements: 3 Enter elements: 802 630 20 745 52 300 612 932 78 187 Data before Sorting: 802 630 20 745 52 300 612 932 78 187 Data after Sorting: 20 52 78 187 300 612 630 745 802 932