Data Structures and Algorithms/Sorting Data/Bucket Sort in C
(Redirected from BucketsortInC)
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* This is a demo program to show how good BucketSort can be. *
* *
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - *
* Copyright (C) 2010 by Ingenieurbüro Henning, Kiel, Germany *
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - *
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published *
* by the Free Software Foundation. *
* *
* This program is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU General Public License for more details. *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
#include <stdio.h>
#define MAXKEYS 100000 // max. number of data records
#define MAXWLNG 25 // max. length of the words in the data record
#define MAXBUCKETS 20 // max. number of buckets
struct FiAd // register of buckets with the star-points in linked lists
{
int StartIndex;// element in linked list where the bucket starts
int LastIndex; // last element of the bucket (to find it fast)
int NumInFifo; // number of references in the fifo
};
struct FiFo // structure of the linked lists used as bucket
{
int PosIndex; // where in the table can this element be found
int Next; // pointer to next element in this bucket
};
struct DataRec // the structure of the test data
{
char TheChar;
short TheShint;
int TheInt;
float TheFloat;
double TheDouble;
int ThePos;
int TheLength;
char TheKey[MAXWLNG + 1];
};
// local subroutines
void BuckSortInt (struct DataRec* Source, struct FiFo* InFif, int Start,
int NumLines, int NumBuckets, int* NewPosis, int* NewPosNr);
void WriteText (char * TextName);
struct DataRec DataRecs [MAXKEYS]; // the input list (unsorted)
struct DataRec SortedRecs [MAXKEYS]; // the sorted output list
int NumRecs; // number of data records
// the input and output files; you have to adapt them to your needs
char In_ListN_1 [40] = "/home/user/EinList.bin";
char OutTextT_2 [40] = "/home/user/BucketSort.txt";
int main(int argc, char *argv[])
{
struct FiFo Positions [MAXKEYS]; // the sequence of records
int NewPosis [MAXKEYS]; // where it is now
int RecLng = sizeof(struct DataRec);// size of one data record
int PosNr = 0; // position to store result
int I, LastInt, NoBuckets;
FILE *fp;
NumRecs = 100000; // number of records to sort
NoBuckets = 7; // number of recursion levels
// we get the input data which we want to sort
fp = fopen(In_ListN_1, "rb");
if(fp != NULL)
{
fread(DataRecs, NumRecs * sizeof(struct DataRec), 1, fp);
fclose(fp);
}
else
{
printf("something is wrong with the file\n");
return;
};
// we set up a linked list with references to all records
for(I = 0; I < NumRecs; I++) // filling linked list
{
Positions[I].PosIndex = I; // record x is at position x
Positions[I].Next = I + 1; // pointer to the next element
};
Positions[I - 1].Next = -1; // end of the linked list
// we indirectly sort the data records; correct sequence will be in NumRecs
BuckSortInt(DataRecs, Positions, 0, NumRecs, NoBuckets, NewPosis, &PosNr);
// we copy the records in correct order to the array SortedRecs
for(I = 0; I < NumRecs; I++)
{
memmove(&SortedRecs[I], &DataRecs[NewPosis[I]], RecLng);
};
// and we check for correct sorting
LastInt = 0x80000000;
for(I = 0; I < NumRecs; I++)
{
if(SortedRecs[I].TheInt < LastInt)
{
printf("sorting not correct\n");
return;
};
LastInt = SortedRecs[I].TheInt;
};
printf("sorting correct\n");
WriteText(OutTextT_2);
}
void BuckSortInt(struct DataRec* Source, struct FiFo* InFif, int Start,
int NumLines, int NumBuckets, int* NewPosis, int* NewPosNr)
{
int I, K, Index, LastLast, FirstFree, Next;
int StepSize, MinVal, MaxVal, ActVal;
long long Interval;
int BuckBorder[MAXBUCKETS]; // border values between buckets
struct FiAd* FifoAdmin; // the fifo administration
struct FiFo* Fifo; // the left fifo
if(NumBuckets > MAXBUCKETS) return;
// we reserve space for the chained lists, depending on length of table
FifoAdmin = (struct FiAd*) malloc(NumBuckets * sizeof(struct FiAd));
Fifo = (struct FiFo*) malloc(NumLines * sizeof(struct FiFo));
for(K = 0; K < NumBuckets; K++)
{
FifoAdmin[K].StartIndex = FifoAdmin[K].LastIndex = -1;
FifoAdmin[K].NumInFifo = 0;
};
FirstFree = 0; // first free element
// now we find the smallest and biggest element for the actual bucket
MinVal = 0x7FFFFFFF; // min. value to biggest value
MaxVal = 0x80000000; // max. value to smallest value
Next = Start; // this is the next element
while(Next >= 0) // while bucket is not empty ...
{
Index = InFif[Next].PosIndex; // next record of this bucket
ActVal = Source[Index].TheInt; // the key value of the record
if(ActVal < MinVal) MinVal = ActVal; // key smaller => swap value
if(ActVal > MaxVal) MaxVal = ActVal; // key bigger => swap value
Next = InFif[Next].Next; // ponter to next element
};
// only identical key values => the record numbers go directly to the result
if(MinVal == MaxVal) // all keys identical ?
{
Next = Start; // this is the next element
while(Next >= 0) // while bucket is not empty ...
{
NewPosis[NewPosNr[0]] = InFif[Next].PosIndex;// final position of record
NewPosNr[0]++; // we point to free element
Next = InFif[Next].Next; // next element of linked list
};
};
// now we make the border-array ready
Interval = (long long) MaxVal - (long long) MinVal; // we get the domain
StepSize = Interval / NumBuckets; // makes chunks of this size
for(I = NumBuckets - 1; I > 0; I--) // loop over the buckets
{
BuckBorder[I] = MaxVal - StepSize; // lower border of the bucket
MaxVal = MaxVal - StepSize; // lower border for next bucket
};
BuckBorder[I] = MinVal; // this way is save
//now we distribute the records of the input bucket to the new sub-buckets
Next = Start; // this is the next element
while(Next >= 0) // while bucket is not empty ...
{
Index = InFif[Next].PosIndex; // next record of this bucket
ActVal = Source[Index].TheInt; // key value of the record
for(I = NumBuckets - 1; I >= 0; I--)
{
if(ActVal >= BuckBorder[I]) // pointing to corrrect bucket?
{
if(FifoAdmin[I].StartIndex < 0) // already entries?
{
// this bucket is used the first time; we start the new linked list
FifoAdmin[I].StartIndex = FirstFree; // start and end
FifoAdmin[I].LastIndex = FirstFree; // are identical
FifoAdmin[I].NumInFifo = 1; // one element in Fifo
Fifo[FirstFree].PosIndex = Index; // number of record to list
Fifo[FirstFree].Next = -1; // no further elements in list
FirstFree++;
}
else
{
// this bucket was already used; we add the reference
LastLast = FifoAdmin[I].LastIndex; // last entry
FifoAdmin[I].NumInFifo++; // one element more in fifo
FifoAdmin[I].LastIndex = FirstFree; // new last element
Fifo[LastLast].Next = FirstFree; // linking ex-last element
Fifo[FirstFree].PosIndex = Index; // the record number
Fifo[FirstFree].Next = -1; // the linked list ends here
FirstFree++;
};
break; // record distributed
};
};
Next = InFif[Next].Next; // next record of actual bucket
};
// we make the recursion and call this function for any subbucket
for(I = 0; I < NumBuckets; I++)
{
if(FifoAdmin[I].NumInFifo > 1)
BuckSortInt(Source, Fifo, FifoAdmin[I].StartIndex,
FifoAdmin[I].NumInFifo, NumBuckets, NewPosis, NewPosNr);
else
if(FifoAdmin[I].NumInFifo == 1)
{
NewPosis[NewPosNr[0]] = Fifo[FifoAdmin[I].StartIndex].PosIndex;
NewPosNr[0]++;
}
};
// we must free the memory we got from the operating system
free(Fifo);
free(FifoAdmin);
};
void WriteText(char * TextName)
{
FILE *fp;
int I;
char TChar;
short TShint;
int TInt;
float TFloat;
double TDouble;
int TPos;
int TLength;
fp = fopen(TextName, "wb");
if(fp != NULL)
{
for(I = 0; I < NumRecs; I++)
{
TChar = SortedRecs[I].TheChar;
TShint = SortedRecs[I].TheShint;
TInt = SortedRecs[I].TheInt;
TFloat = SortedRecs[I].TheFloat;
TDouble = SortedRecs[I].TheDouble;
TPos = SortedRecs[I].ThePos;
TLength = SortedRecs[I].TheLength;
fprintf(fp, "%6d %6d %12d %14e %14e %6d %4d %s\n", TChar,
TShint, TInt, TFloat, TDouble, TPos, TLength, SortedRecs[I].TheKey);
};
fclose(fp);
}
else
{
printf("Ausgabedatei %s kann nicht angelegt werden\n", TextName);
return;
};
};