【數據結構】之用堆實現優先隊列

#include <stdio.h>
#include <malloc.h>

/**
 * 使用堆來實現優先隊列
 * 堆的最重要性質就是子節點的值>=父節點的值,
 * 而且樹的節點是從上到下、從左到右的順序緊湊排列的
 */

//這裏我封裝了一個二叉樹
typedef struct BinaryTree{
    int *note;
    int size;
    void (*push)(struct BinaryTree* , int);
    int (*pop)(struct BinaryTree* );
} BinaryTree;

/**
 * 插入數值
 * 大致思路:首先在二叉樹末尾添加此數值,然後如果它比父節點小就向上提升,
 * 直到不小於父節點或者已經移到根節點爲止
 */
void tree_push(BinaryTree *this, int num){
    int parent = (this->size-1) / 2;
    int curIndex = this->size++;
    while (num < this->note[parent] && curIndex > 0){
        this->note[curIndex] = this->note[parent];
        curIndex = parent;
        parent = (parent-1) / 2;
    }
    this->note[curIndex] = num;
}

/**
 * 刪除最小值
 * 大致思路:根節點就是最小值,把末尾的值賦在根節點上,然後刪除末尾節點,
 * 然後不斷向下交換直到沒有大小顛倒爲止,向下交換中,如果有兩個子節點,
 * 則選擇數值較小的子節點與其進行交換
 */
int tree_pop(BinaryTree *this){
    //最小值
    int ret = this->note[0];
    //末尾的元素
    int x = this->note[--this->size];
    int curIndex = 0;
    int a = curIndex * 2 + 1, b = curIndex * 2 + 2;
    while (x > this->note[a] && a < this->size){
        if (this->note[a] > this->note[b] && b < this->size)
            a = b;
        this->note[curIndex] = this->note[a];
        curIndex = a;
        a = curIndex * 2 + 1, b = curIndex * 2 + 2;
    }
    this->note[curIndex] = x;
    return ret;
}

//初始化
BinaryTree * new_BinaryTree(int max_size){
    BinaryTree *tree = malloc(sizeof(BinaryTree));
    tree->note = malloc(sizeof(int) * max_size);
    tree->size = 0;
    tree->pop = tree_pop;
    tree->push = tree_push;
    return tree;
}

//測試代碼
int main() {
    BinaryTree *tree = new_BinaryTree(1000);
    tree->push(tree, 3);
    tree->push(tree, 1);
    tree->push(tree, 0);
    tree->push(tree, 2);
    tree->push(tree, 2);
    tree->push(tree, 1);
    tree->push(tree, 0);
    tree->push(tree, -1);
    for (int i = 0; i < tree->size; ++i) {
        printf("%d ",tree->note[i]);
    }
    printf("\n");
    tree->pop(tree);
    for (int i = 0; i < tree->size; ++i) {
        printf("%d ",tree->note[i]);
    }

    return 0;
}

運行結果:

-1 0 0 2 2 1 1 3
0 2 0 3 2 1 1