二叉树的层次遍历

/*
 * 读取字符串abcdefghij，然后层次建树建立一颗二叉树，然后中序遍历输出 hdibjeafcg，
 * 后序遍历输出 hidjebfgca，层序遍历输出abcdefghij，注意不要输出汉字*/
#include <stdio.h>
#include <stdlib.h>

#define BiType char
#define ElementType BiTree
typedef struct BiNode{
    BiNode* left;
    BiType data;
    BiNode* right;
}BiNode,*BiTree;

typedef struct LinkNode{
    ElementType data;
    LinkNode* next;
}LinkNode,*LinkList;

typedef struct Queue{
    LinkNode* front;
    LinkNode* rear;
};


void initQueue(Queue &Q){
    LinkList L=(LinkNode*) malloc(sizeof(LinkNode));
    Q.front=Q.rear=L;
}

void EnQueue(Queue &Q,LinkNode* ele){
    LinkNode *NewNode=(LinkNode*) malloc(sizeof(LinkNode));
    NewNode=ele;
    NewNode->next=NULL;
    Q.rear->next=NewNode;
    Q.rear=Q.rear->next;
}

void DeQueue(Queue &Q,LinkNode* &delEle){
    if(Q.rear==Q.front){
        printf("the queue is empty");
    }
    else{
        delEle=Q.front->next;
        free(Q.front);
        Q.front=delEle;
    }
}

bool isEmpty(Queue Q){
    if(Q.front==Q.rear){
        return true;
    }
    else{
        return false;
    }

}

void BuildTree(BiTree &root,Queue &Q){
    root=(BiNode*) malloc(sizeof(BiNode));
    root=Q.front->next->data;
    BiNode *biNode=root;
    //Q.front指向元素为空
    LinkNode *ChildNode=Q.front->next->next;
    LinkNode* delEle;
    while (ChildNode){
        if (!biNode->left){
            biNode->left=ChildNode->data;
            ChildNode=ChildNode->next;
        }
        //需加入判断，防止结束的时候右节点没有孩子，将NULL插入到右节点发生错误
        if (!biNode->right&&ChildNode){
            biNode->right=ChildNode->data;
            ChildNode=ChildNode->next;
        }
        if (biNode->right&&biNode->right){
            DeQueue(Q,delEle);
            biNode=Q.front->next->data;
        }
    }
}

void PreOrder(BiTree tree){
    if (tree){
        printf("%c",tree->data);
        PreOrder(tree->left);
        PreOrder(tree->right);
    }
}

void InOrder(BiTree tree){
    if (tree){
        InOrder(tree->left);
        printf("%c",tree->data);
        InOrder(tree->right);
    }
}

void PostOrder(BiTree tree){
    if(tree){
        PostOrder(tree->left);
        PostOrder(tree->right);
        printf("%c",tree->data);
    }
}

void LevelOrder(BiTree tree,Queue Q){
    BiNode *pNode=tree;
    LinkNode *Node=(LinkNode*) calloc(1,sizeof(LinkNode));
    Node->data=pNode;
    EnQueue(Q, Node);
    LinkNode *delNode;
    while(!isEmpty(Q)){
        DeQueue(Q,delNode);
        printf("%c",delNode->data->data);
        if(pNode->left){
            LinkNode *newNode=(LinkNode*) calloc(1,sizeof(LinkNode));
            newNode->data=pNode->left;
            EnQueue(Q,newNode);
        }
        if(pNode->right){
            LinkNode *newNode1=(LinkNode*) calloc(1,sizeof(LinkNode));
            newNode1->data=pNode->right;
            EnQueue(Q,newNode1);
        }
        //防止队列为空的时候Q.front=Q.rear,Q.front->next->data造成内存泄露
        if(Q.front->next){
            pNode=Q.front->next->data;
        }
    }
    return;
}

int main() {
    Queue Q;
    BiTree tree;
    initQueue(Q);
    char c;
    for(int i=0;i<10;i++){
        LinkNode *Lnode=(LinkNode*) malloc(sizeof(LinkNode));
        BiNode*  Binode=(BiNode*) malloc(sizeof(BiNode));
        scanf("%c",&c);
        Binode->data=c;
        Binode->left=Binode->right=NULL;
        Lnode->data=Binode;
        EnQueue(Q,Lnode);
    }
    BuildTree(tree,Q);
//    PreOrder(tree);
    InOrder(tree);
    printf("\n");
    PostOrder(tree);
    printf("\n");

    Queue Q1;
    initQueue(Q1);
    LevelOrder(tree,Q1);
    return 0;
}