stl_heap

学习一下stl_heap 

         下面的算法是根据stl源码重新整合一下，是为了方便理解

         因为使用的迭代器，为了在给定的迭代器之间使用heap的一些方法，

         内部通常用disHole来确定某个节点 dishole 是指与first距离，可取0 1 2 3 4.....

inline void push_heap(int heap[], int first, int last)
{
    //disHole 指 当前结点 到first的距离 因此距离 是从 0 1 2 3 .....
    int disHole = (last - first) - 1;
    int disHoleParent = (disHole - 1) / 2;
    int value = heap[first+disHole];
    while (disHole> 0 && heap[first + disHoleParent] < value)
    {
        heap[first+disHole] = heap[first+disHoleParent];
        disHole = disHoleParent;
        disHoleParent = (disHole - 1) / 2;
    }
    heap[first + disHole] = value;
}

//调用此方法时 实际上将 最顶 元素 放到了最后
//从上往下调整
inline void pop_heap(int heap[], int first, int last)
{
    int value = heap[last - 1];
    heap[last - 1] = heap[first];
    int disHole = first-first;

    int disSecondHoleChild = (disHole * 2 + 2);
    while (disSecondHoleChild < (last - first - 1))
    {
        if (heap[first + disSecondHoleChild] < heap[first + disSecondHoleChild - 1])
            disSecondHoleChild--;
        heap[first+disHole] = heap[first+disSecondHoleChild];
        disHole = disSecondHoleChild;
        disSecondHoleChild = (disHole * 2 + 2);
    }
    if (disSecondHoleChild == (last - first - 1))
    {
        heap[first + disHole] = heap[first + disSecondHoleChild - 1];
        disHole = disSecondHoleChild - 1;
    }

    heap[first+disHole] = value;
    //这一步，因为在while 循环中，并没有设置让当前大于子女节点时退时
    //所以插入后，使用push_head 进行向上调整
    //当然暂时不理解stl在设计时 为何在while中不进行判断 break
    push_heap(heap, first, disHole + 1);
}
//利用pop_heap 原理实现 排序
inline void sort_heap(int heap[],int first,int last)
{
    while((last-first)>1)
    {
        pop_heap(heap, first, last--);
    }
}
//make_heap 将其调整为最大堆
inline void make_heap(int heap[],int first,int last)
{
    if ((last - first) < 2)return;
    int dislen = last - first - 1;
    int disParent = (dislen - 1) / 2;
    while(true)
    {
        push_heap(heap, first, first + disParent + 1);
        if(disParent==0)return;
        disParent--;
    }
}