自己实现一个可扩容的Heap

今天在公司看stl源码分析，感觉有点无聊。花一个小时写了一个可扩容的Heap，虽然速度很慢，但是写出来的感觉还是很不错的。

#include <iostream>
using namespace std;

class Heap{
public: 
    Heap(int t_size) { //auto_resize
        size = t_size;
        arr = (int *)malloc(sizeof(int) * (t_size) + 1);
        end = 0;
    } 
    
    void resize(int t_size) {
        
        int * t_arr = (int *)malloc(sizeof(int) * (t_size) + 1);
        if (t_size < end) end = t_size;
        
        for (int i = 1; i <= end; ++i) {
            t_arr[i] = arr[i];
        }
        free(arr);
        arr = t_arr;
        size = t_size;
        
    }
    
    void push(int num) {
        if (end == size) {
            resize(2 * size);
        };
        end += 1;
        
        if (end == 1) {
            arr[end] = num;
        }
        //新元素放在完全二叉树的最低端，和父节点比较。如果新元素比父节点大，则它们交换位置。然后新元素再和新的父节点比，直到不能移动为止。
        int cur = end;
        arr[cur] = num;
        while (cur != 1) {
            if (arr[cur] > arr[(int)(cur/2)]) {
                int temp = arr[cur];
                arr[cur] = arr[(int)(cur/2)];
                arr[(int)(cur/2)] = temp;
                
            }
            cur = cur/2;
            
        }
    }
    
    int pop() {
        if (end == 1) {
            end = 0;
            return arr[1];
        }
        
        int res = arr[1];
        int cur = 1;
　　　　　//和末尾的元素交换位置，然后让这个元素往下“坠落”，重新形成一颗新的最大堆
        arr[cur] = arr[end]; 
        while (cur <= end) {
            if (2 * cur + 1 <= end && (arr[cur] < arr[2 * cur] || arr[cur] < arr[2 * cur + 1])) {
                if (arr[2 * cur] > arr[2 * cur + 1]) {
                    int temp = arr[2 * cur];
                    arr[2 * cur] = arr[cur];
                    arr[cur] = temp;
                    cur = 2 * cur;
                }
                else {
                    int temp = arr[2 * cur + 1];
                    arr[2 * cur + 1] = arr[cur];
                    arr[cur] = temp;
                    cur = 2 * cur + 1;
                }
            }
            else if (2 * cur <= end && arr[cur] < arr[2 * cur]) {
                int temp = arr[2 * cur];
                    arr[2 * cur] = arr[cur];
                    arr[cur] = temp;
                    cur = 2 * cur;
            }
            else {
                break;
            }
            
            
        } 
        end -= 1;
        
        return res;
    }
    
    void print() {
        while (end) {
            cout << pop() << " ";
        }
        cout << endl;
    }
    
    void _print() {
        for (int i = 1; i <= size; ++i) {
            cout << arr[i] << " ";
        }
        cout << endl;
    }
private:
    int * arr; 
    int size;
    int end; 
};

int main()
{
    Heap h(10);
    vector<int> ivect{1, 5 ,3, 2, 6, 8, 2, 3};
    for (int i = 0; i < ivect.size(); ++i) {
        h.push(ivect[i]);
    }
    h._print();
    for (int i = 0; i < 10; ++i) {
        h.push(1);
    }
    
    h._print();
    h.resize(7);
    h.print();
    h._print();
    return 0; 
}