# Sort Quick Sort

Source: Internet
Author: User
Tags benchmark

Fast sorting algorithm Quicksort
void QuickSort (Seqlist r,int low,int High)
{//To R[low. High] Quick Sort
int pivotpos;//position of the base record after dividing
if (LowPivotpos=partition (R,low,high);//To R[low. High] do divide
QuickSort (r,low,pivotpos-1);//left-interval recursive sequencing
QuickSort (R,pivotpos+1,high);//Right interval recursive ordering
}
}//quicksort

Attention:
To sort the entire file, just call Quicksort (r,1,n) to complete the r[l. N] the sort.

Partitioning algorithm partition
① Specific procedure
The first step: (initialization) set two pointers I and J, their initial values are the lower and upper bounds of the interval, namely I=low,i=high; Select the first record of the unordered area R[i] (ie R[low]) as the benchmark record, and save it in the variable pivot;
Step two: Let J scan from high to left until the 1th keyword is found to be less than Pivot.key Records R[J], the r[j] is moved to the position I refer to, which is equivalent to r[j] and the base R[i] (that is, pivot) exchanged, A record with a keyword less than the Datum key Pivot.key is moved to the left of the Datum, R[j] is equivalent to pivot, and then the I pointer is scanned to the right from the i+1 position until the 1th keyword is found to be greater than the Pivot.key record R[i], r[i Move to the position I refer to, this is equivalent to exchanging r[i] and datum r[j] so that the record of the keyword greater than the Datum key is moved to the right of the datum, and then the r[i] is equivalent to storing the pivot, and then the pointer J is shifted from position j-1 to the left, so alternating the scanning direction, From each end to the middle, until i=j, I is the benchmark pivot final position, will pivot placed in this position on the completion of a division.
② Partitioning algorithm:
int Partition (seqlist r,int i,int J)
{///call partition (R,low,high), on R[low ... High] do divide,
and returns the location of the base record
Recetype pivot=r[i];//using the 1th record of the interval as the benchmark '
while (I&LT;J) {//From the interval ends alternately to the middle scan, until i=j until
while (I<j&&r[j].key>=pivot.key)//pivot is equivalent to position I
j--//right-to-left scan for 1th keyword less than pivot.key record R[j]
if (i<j)//= keyword found r[j] <pivot.key
R[I++]=R[J];//= Exchange R[i] and r[j], swap i pointer plus 1
while (I<j&&r[i].key<=pivot.key)//pivot is equivalent to position J.
i++//scan from left to right, find 1th keyword greater than Pivot.key record R[i]
if (I&LT;J)//means found r[i], so R[i].key>pivot.key
R[j--]=r[i]; Equivalent to Exchange R[i] and R[j], after the swap J pointer minus 1
}//endwhile
R[i]=pivot//Benchmark record has been last positioned
return i;
}//partition

Instance:

#include <stdio.h>

int part (int a[],int I,int j)
{
int pos=a[i];
while (I&LT;J) {
while (I<j&&a[j]>=pos) j--;
if (i<j) a[i++]=a[j];
while (I<j&&a[i]<=pos) i++;
if (i<j) a[j--]=a[i];
}
A[i]=pos;
return i;
}
void quicksort (int a[], int low, int high)
{
int POS;
if (LowPos=part (A,low,high);
Quicksort (A,LOW,POS-1);
Quicksort (A,pos+1,high);
}
}

int main ()
{
int a={29,48,7,16,325,4,3,22,112,40};
int i;
Quicksort (a,0,9);

printf ("The Out put is\n");
for (i=0;i<10;i++)
printf ("%d\n", A[i]);
return 0;
}

Related Keywords:

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