C++ Program to Implement Bucket Sort

In the Bucket Sorting technique, the data items are distributed of a set of buckets. Each bucket can hold similar type of data. After distributing, each bucket is sorted using another sorting algorithm. After that all elements are gathered into the main list to get the sorted form.

The complexity of Bucket Sort Technique

• Time Complexity: O(n + k) for best case and average case and O(n2 ) for worst case.

• Space Complexity: O(nk) for worst case

Input − A list of unsorted data: 0.25 0.36 0.58 0.41 0.29 0.22 0.45 0.79 0.01 0.69
Output − Array after Sorting: 0.01 0.22 0.25 0.29 0.36 0.41 0.45 0.58 0.69 0.79

Algorithm

bucketSort(array, size)

Input: An array of data, and the total number in the array

Output: The sorted Array

Begin
   for i := 0 to size-1 do
      insert array[i] into the bucket index (size * array[i])
   done
   for i := 0 to size-1 do
      sort bucket[i]
   done
   for i := 0 to size -1 do
      gather items of bucket[i] and put in array
   done
End

Example Code

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
void display(float *array, int size) {
   for(int i = 0; i<size; i++)
      cout << array[i] << " ";
   cout << endl;
}
void bucketSort(float *array, int size) {
   vector<float> bucket[size];
   for(int i = 0; i<size; i++)  {          //put elements into different buckets
      bucket[int(size*array[i])].push_back(array[i]);
   }
   for(int i = 0; i<size; i++) {
      sort(bucket[i].begin(), bucket[i].end());       //sort individual vectors
   }
   int index = 0;
   for(int i = 0; i<size; i++) {
      while(!bucket[i].empty()) {
         array[index++] = *(bucket[i].begin());
         bucket[i].erase(bucket[i].begin());
      }
   }
}
int main() {
   int n;
   cout << "Enter the number of elements: ";
   cin >> n;
   float 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 << "Array before Sorting: ";
   display(arr, n);
   bucketSort(arr, n);
   cout << "Array after Sorting: ";
   display(arr, n);
}

Output

Enter the number of elements: 10
Enter elements:
0.25 0.36 0.58 0.41 0.29 0.22 0.45 0.79 0.01 0.69
Array before Sorting: 0.25 0.36 0.58 0.41 0.29 0.22 0.45 0.79 0.01
0.69
Array after Sorting: 0.01 0.22 0.25 0.29 0.36 0.41 0.45 0.58 0.69
0.79