Question

c-programming quick sort question
why is the value of left and right changing ?

Answer 1

i made it but am stuck in the dry tun :/ help anyone ?

Answer 2

-run

Answer 3

for sanity's sake
```
#include<stdio.h>
#include<conio.h>
void quicksort(int [],int,int);
void main()
{
int value[50],r,a;
clrscr();
printf("\n ENTER RANGE OF YOUR LIST = ");
scanf("%d",&r);
printf("\n \t \t ENTER %d VALUES ",r);
for(a=0;a<r;a++)
{
printf("ENTER %d VALUE = " ,a+1);
scanf("%d",&value[a]);
}
quicksort(value,0,r-1);
printf("\n \t \t THE SORTED SERIES IS : ");
for(a=0;a<r;a++)
printf(" %d ",value[a]);
getch();
}
void quicksort(int value[],int left,int right)
{
int i=left,j=right,pivot=value[left],swap;
while(i<j)
{
while(value[i]<pivot)
i++;
while(value[j]>pivot)
j--;
if(i<=j)
{
swap=value[i];
value[i]=value[j];
value[j]=swap;
i++;
j--;
}
}
if(left<j)
quicksort(value,left,j);
if(right>i)
quicksort(value,i,right);
}
```

Answer 4

sorry bout that ....... can u tell me why are the left and right variable values changing ? the dry run is not as i expected

Answer 5

you might want to use a helper function to partition, I'm comparing your code to some working code right now

Answer 6

i know aboutt the partition function but i can't get it ....... that's why i made this (without partition)

Answer 7

I'm too braindead to step through your code right now. Examine this http://www.comp.dit.ie/rlawlor/Alg_DS/sorting/quickSort.c

Answer 8

ahhh D: the problem is i can never understand other's code so i make up my own logic :/

Answer 9

and now i am stuck ....................

Answer 10

the actual algo is as basic as
```
quicksort(A, i, k):
if i < k:
p := partition(A, i, k)
quicksort(A, i, p - 1)
quicksort(A, p + 1, k)
```

use: quicksort(A, 1, length(A))

Answer 11

which part of the code do you want me to explain

Answer 12

partition and quicksort function

Answer 13

i got the logic but can't do the dry run...........

Answer 14

Let's just step through your code using a sample array
0 5 2 3 4 9 8

Answer 15

ok.