最小堆优先队列C++实现

在建立最小堆或最大堆时。最主要的就是理解。SiftDown和SiftUp算法的实现问题。其实我觉得自己在画一棵树。先比较左右再比较父点之间。是最大堆往上。最小堆往下。就很能理解了，
下面程序是最小堆。
#include <iostream>
using namespace std;

template<class Elem>
class MinHeap
{
private:
Elem* heapArray;
int CurrentSize;
int MaxSize;
public:
MinHeap(const int n);
virtual~ MinHeap()
{
delete []heapArray;
}
void BuildHeap();
bool isLeaf(int pos) const;
int leftChild(int pos) const;
int rightChild(int pos) const;
//return parent position
int parent(int pos) const;
//删除给定下标的元素。
bool Remove(int pos,Elem& node);
void SiftDown(int left);
void SiftUp(int position);
bool Insert(const Elem& newNode);
Elem& RemoveMin();
bool print() const;
};
template<class Elem>
MinHeap<Elem>::MinHeap(const int n)
{
if(n<=0)
return ;
CurrentSize=0;
MaxSize=n;
heapArray=new Elem[MaxSize];
BuildHeap();
}

template<class Elem>
void MinHeap<Elem>::BuildHeap()
{
for(int i=CurrentSize/2-1;i>=0;i--)
SiftDown(i);
}

template<class Elem>
bool MinHeap<Elem>::isLeaf(int pos) const
{
return (pos>=CurrentSize/2) && (pos<CurrentSize);
}

template<class Elem>
int MinHeap<Elem>::leftChild(int pos) const
{
return 2*pos+1;
}

template<class Elem>
int MinHeap<Elem>::rightChild(int pos) const
{
return 2*pos+2;
}

template<class Elem>
int MinHeap<Elem>::parent(int pos) const
{
return (pos-1)/2;
}
//向下筛选。
template<class Elem>
void MinHeap<Elem>::SiftDown(int left)
{
int i=left; 。 //标记父结点
int j=2*i+1;
Elem temp=heapArray[i];

while(j<CurrentSize)
{
if((j<CurrentSize-1) && (heapArray[j]>heapArray[i]))
j++; //指向右子结点
if(temp>heapArray[j])
{
heapArray[i]=heapArray[j];
i=j;
j=2*j+1;
}
else
break;
}
heapArray[i]=temp;
}
//向上筛选
template<class Elem>
void MinHeap<Elem>::SiftUp(int position)
{
int temppos=position;
Elem temp=heapArray[temppos];
while((temppos>0) && (heapArray[parent(temppos)]>temp))
{
heapArray[temppos]=heapArray[parent(temppos)];
temppos=parent(temppos);
}
heapArray[temppos]=temp;
}

template<class Elem>
bool MinHeap<Elem>::Insert(const Elem& newNode)
{
if(CurrentSize==MaxSize)
return false;
heapArray[CurrentSize]=newNode;
SiftUp(CurrentSize);
CurrentSize++;
return true;
}

template<class Elem>
Elem& MinHeap<Elem>::RemoveMin()
{
if(CurrentSize==0)
{
cout<<"Can't Delete ";
}
else
{
Elem temp=heapArray[0];
heapArray[0]=heapArray[CurrentSize-1];
CurrentSize--;
if(CurrentSize>1)
SiftDown(0);
return temp;
}
}

template<class Elem>
bool MinHeap<Elem>::Remove(int pos,Elem& node)
{
if((pos<0) || (pos>CurrentSize))
return false;
Elem temp=heapArray[pos];
heapArray[pos]=heapArray[--CurrentSize];
SiftUp(pos);
SiftDown(pos);
node=temp;
return true;
}

template<class Elem>
bool MinHeap<Elem>::print() const
{
if(CurrentSize<0)
return false;
for(int i=0;i<CurrentSize;i++)
cout<<heapArray[i]<<" ";
return true;
}

int main()
{
MinHeap<char> A(20);
char item;
int pos;
cout<<"Enter 20 number:"<<endl;
for(int i=0;i<20;i++)
{
cout<<"the"<<i<<"NO: ";
cin>>item;
A.Insert(item);
}
cout<<"/nPrint all the number: ";
A.print();
A.RemoveMin();
cout<<"/nAfter delete the Min number:";
A.print();
cout<<"/nEnter the positon you want:";
cin>>pos;
A.Remove(pos,item);
cout<<"/nThe data is:"<<item<<endl;
return 0;
}

//程序示例：
/*
Enter 20 number:
the0NO: a
the1NO: q
the2NO: z
the3NO: w
the4NO: s
the5NO: x
the6NO: e
the7NO: d
the8NO: c
the9NO: r
the10NO: f
the11NO: v
the12NO: t
the13NO: g
the14NO: b
the15NO: y
the16NO: h
the17NO: n
the18NO: u
the19NO: j

Print all the number: a c b d f t e h n j r z v x g y w q u s
After delete the Min number:c f b d r t e h n j s z v x g y w q u
Enter the positon you want:13

The data is:x
*/