快排的递归与非递归

private static void Partition(int[] a,int low,int high){
if(a===null||low>high||low<0||high<0)
return ;
int i=low;int j=high;int point=a[low];
while(i<j){
while(i<j&&a[j]>=point)
j--;
if(i<j)
a[i++]=a[j];a[j]=point;
while(i<j&&a[i]<=point)
i++;
if(i<j)
a[j--]=a[i];a[i]=point;
}
return i;
}

public void QuickSort(int[] a,int low,high){
if(a=null||low<0||high<0||low>high)
return ;
int point=partition(a,low,high);
QuickSort(a,low,point-1);
QuickSort(a,point+1,high);
}

public void QuickSort(int[] a,int low,int high){
if(a=null||low<0||high<0||low>high)
return ;
Stack<Integer> s=new Stack<>();
s.push(low);s.push(high);
while(!s.empty()){
int i=s.peek();
int j=s.peek();
if(i<j){
int k=partition(a,i,j);
if(k>i){
s.push(i);
s.push(k-1);
}else{
s.push(k+1);
s.push(j);
}
}
}