二叉堆的建立

来源：互联网发布：feel软件编辑：程序博客网时间：2024/06/09 17:54

堆是一棵具有特殊性质的二叉树，堆的基本性质是堆中所有结点的值必须大于或者等于（或小于等于）其孩子结点的值。这也称为堆的性质。堆可以分为最大堆和最小堆，如果要求结点的值必须大于其孩子结点的值，则称其为最大堆，反之，则称其为最小堆。

堆在形式上表现为一棵完全二叉树。这里，使用数组来建立一个最大堆：假定下标从0开始，所有元素都保存在数组中

public class Heap {public int[] array;            public int count;              //堆中元素的个数public int capacity;           //堆的大小public int heap_type;          //最小堆或最大堆public Heap(int capacity, int heaptype){this.capacity = capacity;this.heap_type = heaptype;this.count = 0;this.array = new int[capacity];}public int Parent(int i){//通过数组位置的规律得到if(i<=0 || i>this.count)return -1;return (i-1)/2;}public void Print(){for(int i=0;i<this.count;i++)System.out.print(this.array[i]+" ");}//左右孩子public int LeftChild(int i){int left = 2*i+1;if(left>=this.count)return -1;elsereturn left;}public int RightChild(int i){int right = 2*i+2;if(right>=this.count)return -1;return right;}public int GetMaximum(){if(this.count==0)return -1;return this.array[0];}//堆化当前元素public void PercolateDown(int i){int l,r,max,temp;l = LeftChild(i);r= RightChild(i);if (l==-1 && r ==-1)return;if(l != -1 && this.array[l]>this.array[i] )max = l;elsemax = i;if(r!=-1&&this.array[r]>this.array[max])max = r;if(max!=i){temp = this.array[i];this.array[i] = this.array[max];this.array[max] = temp;PercolateDown(max);}}//删除元素public int DeleteMax(){if(this.count==0)return -1;int data = this.array[0];this.array[0] = this.array[this.count-1];this.count--;PercolateDown(0);return data;}//插入元素public int Insert(int data){int i;if(this.count == this.capacity)ResizeHeap();this.count++;i = this.count-1;                if(i==0){            this.array[0] = data;            return i;          }                 while(i>0 && data> this.array[(i-1)/2]){this.array[i] = this.array[(i-1)/2];i=(i-1)/2;}this.array[i] = data;return i;}//扩展堆public void ResizeHeap(){int[] array_old = new int[this.capacity];System.arraycopy(this.array, 0, array_old, 0,this.count-1);this.array = new int[this.capacity*2];if(this.array==null){System.out.println("Memory error");return;}for(int i=0;i<this.capacity;i++)this.array[i] = array_old[i];this.capacity*=2;array_old = null;}//清空堆public void DestroyHeap(){this.count = 0;this.array = null;}//数组建堆，取n个输入元素将它们插入空堆中public void BuildHeap(Heap h,int[] A,int n){if(h==null)return;while(n > this.capacity)h.ResizeHeap();for(int i=0;i<n;i++)h.array[i] = A[i];this.count = n;int max = n-1;for(int i=(max-1)/2;i>=0;i--)h.PercolateDown(i);}}

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