二叉树的层序遍历（先序遍历建树）

#include <iostream>

using namespace std;

typedef struct node
{
    int data;
    struct node *l,*r;
} BT;

BT *creat()
{
    BT *root;
    int temp;
    cin>>temp;// 
　　 // 原来我这里写的是，while(cin>>temp);
    {
        if(temp == -1)
        {
            root = NULL;
        }
        else
        {
            root = new BT;
            root->data = temp;
            root->l = creat();
            root->r = creat();
        }
    }
    return root;
}
void travel(BT *root)
{
    if(root)
    {
        BT *temp[100] = {NULL};
        int in = 0,out = 0;
        temp[in++] = root;
        while(out < in)// 要不要加等号
        {
            if(temp[out]->l != NULL)temp[in++] = temp[out]->l;
            if(temp[out]->r != NULL)temp[in++] = temp[out]->r;
            cout<<temp[out]->data<<endl;
            out++;
        }
    }
    else return;
}
int main()
{
    BT *root = creat();
    travel(root);

    return 0;
}