Bead Sort Algorithm
Bead sort, also named gravity sort, is a natural sorting algorithm, developed by Joshua J. Arulanandham, Cristian S. Calude and Michael J. Dinneen in 2002, and published in The bulletin of the European Association for Theoretical computer Science. Both digital and analogue hardware implementations of bead sort can achieve a sorting time of O(n); however, the implementation of this algorithm tends to be significantly slower in software and can only be used to sort lists of positive integers.
// C++ program to implement gravity/bead sort
#include <stdio.h>
#include <string.h>
using namespace std;
#define BEAD(i, j) beads[i * max + j]
// function to perform the above algorithm
void beadSort(int *a, int len)
{
// Find the maximum element
int max = a[0];
for (int i = 1; i < len; i++)
if (a[i] > max)
max = a[i];
// allocating memory
unsigned char beads[max*len];
memset(beads, 0, sizeof(beads));
// mark the beads
for (int i = 0; i < len; i++)
for (int j = 0; j < a[i]; j++)
BEAD(i, j) = 1;
for (int j = 0; j < max; j++)
{
// count how many beads are on each post
int sum = 0;
for (int i=0; i < len; i++)
{
sum += BEAD(i, j);
BEAD(i, j) = 0;
}
// Move beads down
for (int i = len - sum; i < len; i++)
BEAD(i, j) = 1;
}
// Put sorted values in array using beads
for (int i = 0; i < len; i++)
{
int j;
for (j = 0; j < max && BEAD(i, j); j++);
a[i] = j;
}
}
// driver function to test the algorithm
int main()
{
int a[] = {5, 3, 1, 7, 4, 1, 1, 20};
int len = sizeof(a)/sizeof(a[0]);
beadSort(a, len);
for (int i = 0; i < len; i++)
printf("%d ", a[i]);
return 0;
}
