快速排序

1.快速排序递归原版本

int partition(int *arr,int L,int R)
{
int tmp = arr[L];
while(L<R)
{
while(tmp <= arr[R] && L<R)
{
R--;
}
arr[L] = arr[R];
while(arr[L] <= tmp && L<R)
{
L++;
}
arr[R] = arr[L];

}
arr[L] = tmp;
return L;
}

void quick_sort(int *arr,int L,int R)
{
if (L<R)
{
int base = partition(arr,L,R);
quick_sort(arr,L,base-1);
quick_sort(arr,base+1,R);
}
}

void quick(int *arr,int len)
{
quick_sort(arr,0,len);
}

int main()
{
int arr[] = {8,54,32,15,66,42,34,88,25};
int len = sizeof(arr)/sizeof(arr[0]);
quick(arr,len-1);


   for (int i = 0;i<len;i++)
   {
  printf("%d ",arr[i]);
   }
   printf("\n");
return 0;
}

2..快速排序递归简化版本

void partiion1(int *arr,int L,int R)
{
if (L >= R)
{
return ;
}
int left = L;
int right = R;
int tmp = arr[L];
while(L<R)
{
while(tmp <= arr[R] && L<R)
{
R--;
}
arr[L] = arr[R];
while(arr[L] <= tmp && L<R)
{
L++;
}
arr[R] = arr[L];
}
arr[L] = tmp;

partiion1(arr,left,L-1);
partiion1(arr,L+1,right);
}

void quick_sort1(int *arr,int len)
{
partiion1(arr,0,len);
}

int main()
{
int arr[] = {8,54,32,15,66,42,34,88,25};
int len = sizeof(arr)/sizeof(arr[0]);
quick_sort1(arr,len-1);

for (int i = 0;i<len;i++)
{
printf("%d ",arr[i]);
}
printf("\n");
return 0;
}

3.快速排序 循环版本（利用栈）

int partition(int *arr,int L,int R)
{
int tmp = arr[L];
while(L<R)
{
while(tmp <= arr[R] && L<R)
{
R--;
}
arr[L] = arr[R];
while(arr[L] <= tmp && L<R)
{
L++;
}
arr[R] = arr[L];
}
arr[L] = tmp;
return L;
}

void quick(int *arr,int len)
{
int *stack = (int *)malloc(sizeof(int)*len); 
int top = 0;
stack[top++] = 0;
stack[top++] = len;

while(top !=0 )
{
int R = stack[--top];
int L = stack[--top];
int base = partition(arr,L,R);
if (L<base-1)
{
stack[top++] = L;
stack[top++] = base-1;
}
if (base+1 < R )
{
stack[top++] = base+1;
stack[top++] = R;
}
}
free(stack);
}

int main()
{
int arr[] = {8,54,32,15,66,42,34,88,25};
int len = sizeof(arr)/sizeof(arr[0]);
quick(arr,len-1);


for (int i = 0;i<len;i++)
{
printf("%d ",arr[i]);
}
printf("\n");
return 0;

}