左式堆合并的实现

左式堆合并的实现

源自废弃的 csdn blog

//define the leftist heap struct
typedef struct Leftist pLeftist;
struct Leftist{

    int element;
    pLeftist left, right;
    int npl;
};

//build the merged leftist heap and return it
pLeftist BuildHeap(LeftistQueue q){

    Leftist h1, h2;

    while(!IsEmpty(q)){
        h1 = Dequeue(q);
        if(IsEmpty(q))
            return h1;      //the leftist heap has been built
        h2 = Dequeue(q);

        Enqueue(q, Merge(h1, h2));  //enqueue the new merged leftist heap
    }

    return NULL;    //there is no leftist heap in queue
}

pLeftist Merge(Leftist h1, Leftist h2){

    if(!h1)
        return h2;
    if(!h2)
        return h1;  

    if(h1->elementelement)     //compare the element and choose the root
        return MergeHeap(h1, h2);
    else
        return MergeHeap(h2, h1);
}

pLeftist MergeHeap(Leftist h1, Leftist h2){

    if(!h1->left){
        h1->left = h2;      //single node
    }else{
        h1->right = Merge(h1->right, h2);
        if(h1->left->nplright->npl)    //make left child's npl >= right's
            SwapChl(h1);
        h1->npl = h1->right->npl+1;     //make the npl equalling its right child+1
    }

    return h1;  //return the root
}

分析

• 左式堆而言，较于小根堆

  • 合并速度快，O(n)
  • 链表比数组带来更多的开销，并且多一个域(npl)
  • 代码相对复杂，其实也不复杂

• 较于leftist heap,有个skew heap，每次合并都左右换一下，不需要(npl)，如果数据是随机的，也是一个很不错的选择