最小堆实现优先级队列

#include <iostream>
using namespace std;
class MinHeap{
private:
	int *heap;
	int currentsize;
	int maxsize;
public:
	MinHeap(int sz){
		maxsize=sz;
		heap=new int[maxsize];
		if(heap==NULL){
			cerr<<"distribute error!"<<endl;
			exit(1);
		}
		currentsize=0;
	}
	~MinHeap(){
		delete[]heap;
	}
	bool Insert(const int x);
	bool RemoveMin(int& x);
	bool IsEmpty(){
		return (currentsize==0)?true:false;
	}
	bool IsFull(){
		return (currentsize==maxsize)?true:false;
	}
	void makeEmpty(){
		currentsize=0;
	}
	void shiftdown(int start);
	void shiftup(int start);
};
void MinHeap::shiftdown(int start){
	int i=start;
	int j=(heap[i*2+1]<heap[i*2+2])?i*2+1:i*2+2;
	int temp=heap[start];
	while(j<currentsize){
		if(temp<=heap[j]){
			break;
		}
		heap[i]=heap[j];
		i=j;
		j=(heap[i*2+1]<heap[i*2+2])?i*2+1:i*2+2;
	}
	heap[i]=temp;
}
void MinHeap::shiftup(int start){
	int i=start;
	int j=(i-1)/2;
	int temp=heap[i];
	while(i>0){
		if(temp>=heap[j]){
			break;
		}
		if(temp<heap[j]){
			heap[i]=heap[j];
			i=j;
			j=(i-1)/2;
		}
	}
	heap[i]=temp;
}
bool MinHeap::Insert(const int x){
	if(IsFull()){
		cerr<<"Heap Full"<<endl;
		return false;
	}
	heap[currentsize]=x;
	shiftup(currentsize);
	currentsize++;
	return true;
}
bool MinHeap::RemoveMin(int& x){
	if(IsEmpty()){
		cerr<<"Heap Empty"<<endl;
		return false;
	}
	x=heap[0];
	heap[0]=heap[currentsize-1];
	shiftdown(0);
	currentsize--;
	return true;
}
int main(){
	MinHeap t(1002);
	cout<<"Insert 1 Remove 2 Exit 3"<<endl;
	int f;
	while(1){
		cin>>f;
		if(f==1){
			int num,c;
			cout<<"number of num:";
			cin>>c;
			while(c--){
				cin>>num;
				if(t.Insert(num)){
				    cout<<"Success!"<<endl;
			    }
			}
		}
		else if(f==2){
			int x;
			if(t.RemoveMin(x)){
				cout<<"The Min num:"<<x<<endl;
			}
		}
		else if(f==3){
			break;
		}
		else{
			cout<<"Your input is illegal"<<endl;
			break;
		}
	}
	return 0;
}