算法-堆排序

#include<iostream>
#include<algorithm>
using namespace std;
long save[50010];
long savei = 1;
inline void sawp(long &a, long &b)
{
    long temp = a;
    a = b;
    b = temp;
}
bool judgeIFfix(long arr[], long node, long n)
{
    if (2 * node > n) return false;//没有子节点，返回false
    if (arr[node] < arr[2 * node]) return true;//左节点比它大，返回true
    if (2 * node + 1 <= n)//存在右节点
    {
        if (arr[node] < arr[2 * node + 1]) return true;//右节点比它大，返回true
    }
    return false;//不存在子节点比它大，返回false
}
void max_heapify(long arr[],long node, long n)
{
    if (2 * node > n) return;//判断node是否有子节点，没有就返回
    long largest;
    if (arr[node] < arr[2 * node]) largest = 2 * node;
    else largest = node;
    if (2 * node + 1 <= n)//右节点都没有超出范围n，左节点已在上边处理
    {
        if (arr[largest] < arr[2 * node + 1]) largest = 2 * node + 1;
    }
    if (largest != node) swap(arr[node], arr[largest]);
    if (judgeIFfix(arr,2*node,n)) max_heapify(arr, 2 * node, n);//判断node的左节点是否需要fix、
    if (judgeIFfix(arr,2*node+1,n)) max_heapify(arr, 2 * node + 1, n);//判断node的右节点是否需要fix
}
void heapsort(long arr[], long n)
{
    long lastfather = (n + 1) / 2;
    for (long i = lastfather; i >= 1; i--)//生成最大堆
        max_heapify(arr, i, n);

    for (long i = n; i >=1; i--)
    {
        save[savei++] = arr[1];//每次从堆中选取最大元素
        swap(arr[i], arr[1]);//将最大元素与最后一个元素交换
        max_heapify(arr, 1, i-1);
    }
}
int main()
{
    long n, arr[50010];
    cin >> n;
    for (long i = 1; i <= n; i++)
        cin >> arr[i];
    heapsort(arr, n);
    for (long i = savei - 1; i >= 1; i--)
        cout << save[i] << endl;
    system("pause");
    return 0;
}