Bucket Sort To Sort an Array with Negative Numbers
Last Updated : 31 Jan, 2023
We have discussed bucket sort in the main post on Bucket Sort .
Bucket sort is mainly useful when input is uniformly distributed over a range. For example, consider the problem of sorting a large set of floating point numbers which are in range from 0.0 to 1.0 and are uniformly distributed across the range. In the above post, we have discussed Bucket Sort to sort numbers which are greater than zero.
How to modify Bucket Sort to sort both positive and negative numbers?
Example:
Input : arr[] = { -0.897, 0.565, 0.656, -0.1234, 0, 0.3434 } Output : -0.897 -0.1234 0 0.3434 0.565 0.656 Here we considering number is in range -1.0 to 1.0 (floating point number)
Algorithm :
sortMixed(arr[], n) 1) Split array into two parts create two Empty vector Neg[], Pos[] (for negative and positive element respectively) Store all negative element in Neg[] by converting into positive (Neg[i] = -1 * Arr[i] ) Store all +ve in pos[] (pos[i] = Arr[i]) 2) Call function bucketSortPositive(Pos, pos.size()) Call function bucketSortPositive(Neg, Neg.size()) bucketSortPositive(arr[], n) 3) Create n empty buckets (Or lists). 4) Do following for every array element arr[i]. a) Insert arr[i] into bucket[n*array[i]] 5) Sort individual buckets using insertion sort. 6) Concatenate all sorted buckets.
Below is implementation of above idea (for floating point number )
CPP // C++ program to sort an array of positive // and negative numbers using bucket sort #include <bits/stdc++.h> using namespace std; // Function to sort arr[] of size n using // bucket sort void bucketSort(vector<float> &arr, int n) { // 1) Create n empty buckets vector<float> b[n]; // 2) Put array elements in different // buckets for (int i=0; i<n; i++) { int bi = n*arr[i]; // Index in bucket b[bi].push_back(arr[i]); } // 3) Sort individual buckets for (int i=0; i<n; i++) sort(b[i].begin(), b[i].end()); // 4) Concatenate all buckets into arr[] int index = 0; arr.clear(); for (int i = 0; i < n; i++) for (int j = 0; j < b[i].size(); j++) arr.push_back(b[i][j]); } // This function mainly splits array into two // and then calls bucketSort() for two arrays. void sortMixed(float arr[], int n) { vector<float>Neg ; vector<float>Pos; // traverse array elements for (int i=0; i<n; i++) { if (arr[i] < 0) // store -Ve elements by // converting into +ve element Neg.push_back (-1 * arr[i]) ; else // store +ve elements Pos.push_back (arr[i]) ; } bucketSort(Neg, (int)Neg.size()); bucketSort(Pos, (int)Pos.size()); // First store elements of Neg[] array // by converting into -ve for (int i=0; i < Neg.size(); i++) arr[i] = -1 * Neg[ Neg.size() -1 - i]; // store +ve element for(int j=Neg.size(); j < n; j++) arr[j] = Pos[j - Neg.size()]; } /* Driver program to test above function */ int main() { float arr[] = {-0.897, 0.565, 0.656, -0.1234, 0, 0.3434}; int n = sizeof(arr)/sizeof(arr[0]); sortMixed(arr, n); cout << "Sorted array is \n"; for (int i=0; i<n; i++) cout << arr[i] << " "; return 0; } // Java program to sort an array of positive // and negative numbers using bucket sort import java.util.*; class GFG { // Function to sort arr[] of size n using // bucket sort static void bucketSort(Vector<Double> arr, int n) { // 1) Create n empty buckets @SuppressWarnings("unchecked") Vector<Double> b[] = new Vector[n]; for (int i = 0; i < b.length; i++) b[i] = new Vector<Double>(); // 2) Put array elements in different // buckets for (int i = 0; i < n; i++) { int bi = (int)(n*arr.get(i)); // Index in bucket b[bi].add(arr.get(i)); } // 3) Sort individual buckets for (int i = 0; i < n; i++) Collections.sort(b[i]); // 4) Concatenate all buckets into arr[] int index = 0; arr.clear(); for (int i = 0; i < n; i++) for (int j = 0; j < b[i].size(); j++) arr.add(b[i].get(j)); } // This function mainly splits array into two // and then calls bucketSort() for two arrays. static void sortMixed(double arr[], int n) { Vector<Double>Neg = new Vector<>(); Vector<Double>Pos = new Vector<>(); // traverse array elements for (int i = 0; i < n; i++) { if (arr[i] < 0) // store -Ve elements by // converting into +ve element Neg.add (-1 * arr[i]) ; else // store +ve elements Pos.add (arr[i]) ; } bucketSort(Neg, (int)Neg.size()); bucketSort(Pos, (int)Pos.size()); // First store elements of Neg[] array // by converting into -ve for (int i = 0; i < Neg.size(); i++) arr[i] = -1 * Neg.get( Neg.size() -1 - i); // store +ve element for(int j = Neg.size(); j < n; j++) arr[j] = Pos.get(j - Neg.size()); } /* Driver program to test above function */ public static void main(String[] args) { double arr[] = {-0.897, 0.565, 0.656, -0.1234, 0, 0.3434}; int n = arr.length; sortMixed(arr, n); System.out.print("Sorted array is \n"); for (int i = 0; i < n; i++) System.out.print(arr[i] + " "); } } // This code is contributed by Rajput-Ji # Python3 program to sort an array of positive # and negative numbers using bucket sort # Function to sort arr[] of size n using # bucket sort def bucketSort(arr, n): # 1) Create n empty buckets b = [] for i in range(n): b.append([]) # 2) Put array elements in different # buckets for i in range(n): bi = int(n*arr[i]) b[bi].append(arr[i]) # 3) Sort individual buckets for i in range(n): b[i].sort() # 4) Concatenate all buckets into arr[] index = 0 arr.clear() for i in range(n): for j in range(len(b[i])): arr.append(b[i][j]) # This function mainly splits array into two # and then calls bucketSort() for two arrays. def sortMixed(arr, n): Neg = [] Pos = [] # traverse array elements for i in range(n): if(arr[i]<0): # store -Ve elements by # converting into +ve element Neg.append(-1*arr[i]) else: # store +ve elements Pos.append(arr[i]) bucketSort(Neg,len(Neg)) bucketSort(Pos,len(Pos)) # First store elements of Neg[] array # by converting into -ve for i in range(len(Neg)): arr[i]=-1*Neg[len(Neg)-1-i] # store +ve element for i in range(len(Neg),n): arr[i]= Pos[i-len(Neg)] # Driver program to test above function arr = [-0.897, 0.565, 0.656, -0.1234, 0, 0.3434] sortMixed(arr, len(arr)) print("Sorted Array is") print(arr) # This code is contributed by Pushpesh raj // C# program to sort an array of positive // and negative numbers using bucket sort using System; using System.Collections.Generic; public class GFG { // Function to sort []arr of size n using // bucket sort static void bucketSort(List<Double> arr, int n) { // 1) Create n empty buckets List<Double> []b = new List<Double>[n]; for (int i = 0; i < b.Length; i++) b[i] = new List<Double>(); // 2) Put array elements in different // buckets for (int i = 0; i < n; i++) { int bi = (int)(n*arr[i]); // Index in bucket b[bi].Add(arr[i]); } // 3) Sort individual buckets for (int i = 0; i < n; i++) b[i].Sort(); // 4) Concatenate all buckets into []arr int index = 0; arr.Clear(); for (int i = 0; i < n; i++) for (int j = 0; j < b[i].Count; j++) arr.Add(b[i][j]); } // This function mainly splits array into two // and then calls bucketSort() for two arrays. static void sortMixed(double []arr, int n) { List<Double>Neg = new List<Double>(); List<Double>Pos = new List<Double>(); // traverse array elements for (int i = 0; i < n; i++) { if (arr[i] < 0) // store -Ve elements by // converting into +ve element Neg.Add (-1 * arr[i]) ; else // store +ve elements Pos.Add (arr[i]) ; } bucketSort(Neg, (int)Neg.Count); bucketSort(Pos, (int)Pos.Count); // First store elements of Neg[] array // by converting into -ve for (int i = 0; i < Neg.Count; i++) arr[i] = -1 * Neg[ Neg.Count -1 - i]; // store +ve element for(int j = Neg.Count; j < n; j++) arr[j] = Pos[j - Neg.Count]; } /* Driver program to test above function */ public static void Main(String[] args) { double []arr = {-0.897, 0.565, 0.656, -0.1234, 0, 0.3434}; int n = arr.Length; sortMixed(arr, n); Console.Write("Sorted array is \n"); for (int i = 0; i < n; i++) Console.Write(arr[i] + " "); } } // This code is contributed by Rajput-Ji function bucketSort(arr, n) { // 1) Create n empty buckets var b = new Array(n); for (var i = 0; i < n; i++) { b[i] = []; } // 2) Put array elements in different buckets for (var i = 0; i < n; i++) { var bi = Math.floor(n * arr[i]); // Index in bucket b[bi].push(arr[i]); } // 3) Sort individual buckets for (var i = 0; i < n; i++) { b[i].sort(); } // 4) Concatenate all buckets into arr[] var index = 0; arr.length = 0; for (var i = 0; i < n; i++) { for (var j = 0; j < b[i].length; j++) { arr.push(b[i][j]); } } } // This function mainly splits array into two // and then calls bucketSort() for two arrays. function sortMixed(arr, n) { var Neg = []; var Pos = []; // traverse array elements for (var i = 0; i < n; i++) { if (arr[i] < 0) { // store -Ve elements by converting into +ve element Neg.push(-1 * arr[i]); } else { // store +ve elements Pos.push(arr[i]); } } bucketSort(Neg, Neg.length); bucketSort(Pos, Pos.length); // First store elements of Neg[] array // by converting into -ve for (var i = 0; i < Neg.length; i++) { arr[i] = -1 * Neg[Neg.length - 1 - i]; } // store +ve element for (var j = Neg.length; j < n; j++) { arr[j] = Pos[j - Neg.length]; } } /* Driver program to test above function */ (function main() { var arr = [-0.897, 0.565, 0.656, -0.1234, 0, 0.3434]; var n = arr.length; sortMixed(arr, n); console.log("Sorted array is"); for (var i = 0; i < n; i++) { console.log(arr[i] + " "); } })(); OutputSorted array is -0.897 -0.1234 0 0.3434 0.565 0.656
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