2.5 k个最大的数

#include <string.h>
#include <stdio.h>


void Swap(int * a, int i, int j)
{
    int temp = a[i];
    a[i] = a[j];
    a[j] = temp;
}

void Heapify(int * a, int start, int end)
{
    int index;
    if (2 * start + 2 <= end) {
        index = a[2 * start + 1] < a[2 * start + 2] ? (2 * start + 1) : (2 * start + 2);
        if (a[index] < a[start]) {
            Swap(a, index, start);
            Heapify(a, index, end);
        }
    } else if (2 * start + 1 == end) {
        if (a[2 * start + 1] < a[start]) {
            Swap(a, 2 * start + 1, start);
        }
    }
}

template <int MAX = 3>
class KBigHeap {
private:
    int data[MAX];
    int cur;
public:
    KBigHeap():cur(0)
    {}
    void Insert(int n)
    {
        if (cur < MAX) {
            data[cur++] = n;
        } else {
         if (cur == MAX) { // 前面的刚刚满，要构造堆
                int i;
                for (i = (MAX - 1) / 2; i >= 0; --i) {
                    Heapify(data, i, MAX - 1);
                }
                ++cur;
            }
            if (n > data[0]) {
                data[0] = n;
                Heapify(data, 0, MAX - 1);
            }
        }
    }
    
    void Handle(int * a, int n)
    {
        int i;
        for (i = 0; i < n; ++i) {
            Insert(a[i]);
        }
    }

    void Print() const
    {
        int i;
        for (i = 0; i < MAX; ++i) {
            printf("%3d", data[i]);
        }
        printf("\n");
    }

};


int main()
{
    int a[10] = {1, 9, 8, 7, 3, 5, 6, 2, 0, 4};
    KBigHeap<5> k;
    k.Handle(a, 10);

    k.Print();

    return 0;
}