程序代码：

#include <stdio.h>
#include <malloc.h>
struct tree{
    char data;
    struct tree *lchild,*rchild;
};
struct tree *create(struct tree *tree){
    char ch;
    scanf(" %c",&ch);
    if(ch=='#')
        tree=NULL;
    else{   
        tree=(struct tree *)malloc(sizeof(struct tree));
        tree->data=ch;
        tree->lchild=create(tree->lchild);
        tree->rchild=create(tree->rchild);
    }
    return tree;
}
void levelorder(struct tree *tree){
    struct tree *a[100];
    int rear=0,front=0;
    if(tree){
        a[rear++]=tree;
        while(front!=rear){
            printf("%2c",a[front]->data);
            if(a[front]->lchild)
                a[rear++]=tree->lchild;
            if(a[front]->rchild)
                a[rear++]=tree->rchild;
            front++;
        }
    }
}
void main(){
    struct tree *t;
    printf("输入节点值(按照先序遍历输入)");
    t=create(t);
    printf("按层遍历(队列):");
    levelorder(t);
}