Algorithms |
Bin Sort |
Assume that
For example, if we wish to sort 104 32-bit integers,
then m = 232 and we need 232
operations (and a rather large memory!).
For n = 104:
An implementation of bin sort might look like:
#define EMPTY -1 /* Some convenient flag */ void bin_sort( int *a, int *bin, int n ) { int i; /* Pre-condition: for 0<=i<n : 0 <= a[i] < M */ /* Mark all the bins empty */ for(i=0;i<M;i++) bin[i] = EMPTY; for(i=0;i<n;i++) bin[ a[i] ] = a[i]; } main() { int a[N], bin[M]; /* for all i: 0 <= a[i] < M */ .... /* Place data in a */ bin_sort( a, bin, N );
If there are duplicates, then each bin can be replaced by a linked list. The third step then becomes:
In contrast to the other sorts, which sort in place and don't require additional memory, bin sort requires additional memory for the bins and is a good example of trading space for performance.
so that we would normally use memory rather profligately to obtain performance, memory consumes power and in some circumstances, eg computers in space craft, power might be a higher constraint than performance. |
Having highlighted this constraint, there is a version of bin sort which can sort in place:
#define EMPTY -1 /* Some convenient flag */ void bin_sort( int *a, int n ) { int i; /* Pre-condition: for 0<=i<n : 0 <= a[i] < n */ for(i=0;i<n;i++) if ( a[i] != i ) SWAP( a[i], a[a[i]] ); }
The bin sorting strategy may appear rather limited, but it can be generalised into a strategy known as Radix sorting.
Continue on to Radix sorting |