【数据结构】 C++实现最大堆

参考浙大陈越姥姥数据结构

#include 
#include 
#include 
using namespace std;
#define maxsize 100

typedef struct hnode* heap;
struct hnode{
    int* arr;
    int size;
    int capacity;
};

heap init_heap() {
    heap H = new hnode;
    H->size = 0;
    H->capacity = maxsize;
    H->arr = new int[H->capacity];
    H->arr[0] = INT_MAX;            // 最大堆，哨兵

    return H;
}

int delete_elem(heap H) {       // 每次弹出最大元素
    if(H->size == 0) {
        cout << "Heap is empty :((" << endl;
        return -1;
    }
    int child, parent;
    int last_elem = H->arr[H->size--];
    int ret = H->arr[1];
    int n = H->size;
    for(parent=1; parent*2<=n; parent=child) {
        child=parent*2;
        if(child+1<=n && H->arr[child+1]>H->arr[child])
            child++;
        if(H->arr[child] < last_elem)
            break;
        else
            H->arr[parent] = H->arr[child];
    }
    H->arr[parent] = last_elem;
    return ret;
}


void adjust(heap H, int i) {      // 最大堆
    int child, parent;
    int last_elem = H->arr[i];
    int n = H->size;
    for(parent=i; parent*2<=n; parent=child) {
        child = parent*2;
        if(child+1 <= n && H->arr[child+1] > H->arr[child]) 
            child++;
        if(H->arr[child] < last_elem) 
            break;
        else 
            H->arr[parent] = H->arr[child];
    }
    H->arr[parent] = last_elem;
}

void build_heap(heap H) {
    int n = H->size;
    for(int i=n/2; i>0; i--) 
        adjust(H, i);
} 

int main()
{
    heap H = init_heap();
    vector nums = {8,6,3,2,1,7,5,9,4};       // 要调整为最大堆的数组
    for(int i=0; i
        H->arr[i+1] = nums[i];
        H->size++;
    }
    
    // O(n)建立heap
    build_heap(H);


    for(int i=0; i<10; i++)        // 9个元素，最后一次应该是-1
        cout << delete_elem(H) << endl;



    return 0;
}