1123. Is It a Complete AVL Tree (30) PAT 甲级

传送门

用bfs去层次遍历。
当bfs到NULL值时但是所有的节点并没有遍历完时，说明不是完全二叉树

#include<stdio.h>#include<algorithm>#include<queue>using namespace std;typedef struct Node{    int weight;    int height;    Node *lchild,*rchild;}AVLnode,*AVLtree;AVLtree root;int n;AVLnode *newNode(int weight){    AVLnode *node=new AVLnode;    node->weight=weight;    node->height=1;    node->lchild=node->rchild=NULL;    return node;}int getHeight(AVLtree root){    if(root==NULL)  return 0;    return root->height;}void updateHeight(AVLtree root){    root->height=max(getHeight(root->lchild),getHeight(root->rchild))+1;}int getBalanceFactor(AVLtree root){    return getHeight(root->lchild)-getHeight(root->rchild);}void L(AVLtree &root){    AVLnode *temp=root->rchild;    root->rchild=temp->lchild;    temp->lchild=root;    updateHeight(root);    updateHeight(temp);    root=temp;}void R(AVLtree &root){    AVLnode *temp=root->lchild;    //root->lchild=temp->lchild;    root->lchild=temp->rchild;    temp->rchild=root;    updateHeight(root);    updateHeight(temp);    root=temp;}void insert(AVLtree &root,int weight){    if(root==NULL){        root=newNode(weight);        return;    }    if(weight<root->weight){        insert(root->lchild,weight);        updateHeight(root);        if(getBalanceFactor(root)==2){            if(getBalanceFactor(root->lchild)==1){                R(root);            }            else if(getBalanceFactor(root->lchild)==-1){                L(root->lchild);                R(root);            }        }    }    else{        insert(root->rchild,weight);        updateHeight(root);        if(getBalanceFactor(root)==-2){            if(getBalanceFactor(root->rchild)==-1){                L(root);            }            else if(getBalanceFactor(root->rchild)==1){                R(root->rchild);                L(root);            }        }    }}bool bfs(AVLnode *root){    int count=0;    queue<AVLnode*> q;    q.push(root);    bool flag=true;    while(count<n){        AVLnode* p=q.front();        q.pop();        if(p!=NULL){            printf("%d",p->weight);            count++;            if(count!=n){                printf(" ");            }            else{                printf("\n");            }            q.push(p->lchild);            q.push(p->rchild);        }        else{            if(count<n){                flag=false;            }        }    }    return flag;}int main(){    int weight;    scanf("%d",&n);    for(int i=0;i<n;i++){        scanf("%d",&weight);        insert(root,weight);    }    //printf("%d",root->weight);    bool flag=bfs(root);    if(flag)        printf("YES");    else        printf("NO");}