堆排序

堆类似一颗完全二叉树，根节点是一个最值，同时它的左右两颗子树也是堆。下面以最大堆为例，插入操作跟插入排序是一样的，把新加入的节点放到树的最后面，然后跟它的父亲比较，如果比父亲比它小，则互换位置，直到找到某个祖先节点大于它时停止。取最大值则直接取根节点，若删去该节点，则要重新调整堆，使得该堆仍是最大堆。做法是把树中最后一个节点放到根节点，然后向下查找，跟其值最小的孩子互换位置，直到找到一个大于它的子孙节点便终止。

 

#include <iostream>#include <cstdio>#include <cstring>#include <ctime>#include <cstdlib>using namespace std;void update_down(int *heap,int pos,int sum){    int tem = heap[pos];    int son = pos<<1;    while(son <= sum)    {        if(son < sum && heap[son] < heap[son+1])            son++;        if(heap[son] > tem)        {            heap[pos] = heap[son];            pos = son, son = pos<<1;        }        else            break;    }    heap[pos] = tem;}void update_up(int *heap,int pos,int sum){    int tem = heap[pos];    int father = pos>>1;    while(father > 0 && heap[father] < tem)    {        heap[pos] = heap[father];        pos = father, father = pos>>1;    }    heap[pos] = tem;}int main(){    int len, *heap;    cin >> len;    heap = new int [len+1];    srand((int)time(0));    int startTime = clock();    for(int i=1; i<=len; i++)    {        heap[i] = rand()%512 + 1;        update_up(heap,i,i);    }    int sum = len;    while(sum)    {       // cout << heap[1] << " ";        heap[1] = heap[sum--];        update_down(heap,1,sum);    }    int endTime = clock();    cout << "\nused time: " << endTime - startTime << endl;}