源代码：

#include <iostream>
#include <cstdlib>
#include <queue>
using namespace std;

typedef struct Node {
    char root;
    struct Node *lchild;
    struct Node *rchild;
} *Tree;

//广度优先遍历
void breadthFirstSearch(Tree root)
{
    if (!root)
    {
        return;
    }
    queue<Node *> nodeQueue;
    nodeQueue.push(root);
    Node *node;
    while(!nodeQueue.empty())
    {
        node = nodeQueue.front();
        nodeQueue.pop();
        cout << node->root << " ";

        if(node->lchild)
        {
            nodeQueue.push(node->lchild);  //先将左子树入队
        }

        if(node->rchild)
        {
            nodeQueue.push(node->rchild);  //再将右子树入队
        }
    }
}

//创建二叉树
void CreateBtree(Tree * T)
{
    char ch;
    cout << "请输入字符：（输入#表示为空!)" << endl;
    cin >> ch;

    if (ch == '#')
    {
        *T = NULL;
    }
    else
    {
        *T = (Tree)malloc(sizeof(Node));
        (*T)->root = ch;

        CreateBtree(&(*T)->lchild);
        CreateBtree(&(*T)->rchild);
    }
}

void releasetree(Tree T)
{
    if (T)
    {
        releasetree(T->lchild);
        releasetree(T->rchild);
        free(T);
        T == NULL;
    }
}

int main()
{
    Tree  T;
    
    CreateBtree(&T);

    breadthFirstSearch(T);

    releasetree(T);

    return 0;
}

运行结果截图：