[算法练习]快速排序的C语言实现

#include <stdio.h>

void quick_sort(int A[],int p,int r){
if(p<r){
int q=partition(A,p,r);
quick_sort(A,p,q-1);
quick_sort(A,q+1,r);
}
}
int times=0;
//basic function of quick sort
int partition(int A[],int p,int r){
/*	assume A[r] as the benchmark;
while A[cur] is move from A[p] to A[r]:
if A[cur] is smaller than A[r],	then exchange A[par] and A[cur];
A[cur] move to next;
at last, exchange A[r] and A[par];
so that A[par] is sorted in the array A[],
because the numbers before A[par] is smaller than it,
and the numbers after A[par] is larger than it.
*/
int cur=p,par=p;
while(cur<r){
if(A[cur]<A[r]){
//exchange A[cur] and A[par] then par++
int temp=A[cur];
A[cur]=A[par];
A[par]=temp;
par++;
}
cur++;
}
//exchange A[r] and A[par]
int temp=A[r];
A[r]=A[par];
A[par]=temp;
printf("\nafter %d times:\t",++times);
int i;
for(i=0;i<10-1;i++){
printf("%d ",A[i]);
}
return par;
}

int main(){
int a[]={3,1,5,12,6,8,11,7,4,15};
int length=sizeof(a)/sizeof(a[0]);//get length of a[]

int i;
printf("before:\t");
for(i=0;i<length;i++){
printf("%d ",a[i]);
}
quick_sort(a,0,length-1);
printf("\nafter:\t");
for(i=0;i<length;i++){
printf("%d ",a[i]);
}
getchar();
}