详解基于堆的基本操作

constint maxheapsize=100;
staticint currentsize=0;

//从上到下调整堆
void siftDown(int* heap,int currentPos,int m)
{
    int i=currentPos;
    int j=currentPos*2+1;//i's leftChild
int temp=heap[i];
    while(j<=m)
    {
        if(j<m&&heap[j]>heap[j+1]) j++;// j points to minChild
if(temp<=heap[j]) break;
        else
        {
            heap[i]=heap[j];
            i=j;
            j=2*i+1;
        }
    }
    heap[i]=temp;
}

//从下向上调整堆
void siftUp(int* heap, int start)
{
    int i=start,j=(i-1)/2;
    int temp=heap[i];

    while(i>0)
    {
        if(heap[j]>temp)
        {
            heap[i]=heap[j];
            i=j;
            j=(i-1)/2;
        }
        elsebreak;
    }
    heap[i]=temp;
}

//构建堆
int* Heap(int*arr, int size)
{
    int i;
    currentsize=size;
    int* heap =newint[maxheapsize];
    assert(heap!=NULL);
    for(i=0;i<currentsize;i++) heap[i]=arr[i];
    int currentPos=(currentsize-2)/2;
    while(currentPos>=0)
    {
        siftDown(heap,currentPos,currentsize-1);
        currentPos--;
    }
    return heap;
}

//增加一个元素
void insert(int* heap,int value)
{
    if(currentsize>=maxheapsize)
    {
        cout<<"Heap is full!"<<endl;
        return ;
    }
    heap[currentsize]=value;
    siftUp(heap,currentsize);
    currentsize++;
}

//删除一个元素,并返回删除前的堆顶元素
int removemin(int* heap)
{
    assert(currentsize>=0);
    int removeValue=heap[0];
    heap[0]=heap[currentsize-1];
    currentsize--;
    siftDown(heap,0,currentsize-1);
    return removeValue;
}

int main()
{
    constint size=10;
    int arr[size]={2,1,3,0,8,1,6,9,7,10};
    int* heap=Heap(arr,size);
    //堆排序
for(int i=0;i<size;i++)
    {
        arr[i]=removemin(heap);
        cout<<arr[i]<<endl;
    }
    delete []heap;
    return0;

 
 

}