先序构造二叉树、层次遍历输出

#include<iostream>
#include<queue>
using namespace std;
 
//树结构定义 
typedef struct node{
    char val;
    struct node* left;
    struct node* right;
}TreeNode,*Tree;
 
//先序构造二叉树 
void CreateTree(Tree& t){
    char x;
    cin>>x;
    if(x == '.') t = NULL; //遇到'#',t置空 
    else{
        t = new TreeNode; //创建一个新结点，让t指向它 
        t->val = x; //新结点赋值x 
        CreateTree(t->left); //递归的创建左结点 
        CreateTree(t->right); //递归的创建右结点 
    }
} 
 
//层次遍历输出二叉树 
void levelOrder(Tree& t) {
    if(t == NULL) return;
    queue<TreeNode*> q;
    q.push(t);
    while(!q.empty()){
        int n = q.size();
        for(int i = 0;i<n;i++){
            TreeNode* s = q.front();
            cout<<s->val<<" ";
            q.pop();
            if(s->left) q.push(s->left);
            if(s->right) q.push(s->right);
        }
        cout<<endl;
    } 
}
 
int main(){
    Tree t;
    CreateTree(t);
    /*
       a b d # # e # # c f # # #
    */
    levelOrder(t); 
}