题目：输入一颗二元树，从上往下按层打印树的每个结点，同一层中按照从左往右的顺序打印。
例如输入
8
/ \
6 10
/\ /\
5 7 9 11
输出8 6 10 5 7 9 11。
#include <iostream>
#include <deque>
using namespace std;
struct tree
{
int value;
tree *left;
tree *right;
};
void addTree(tree *&ptr,int value)
{
if (ptr==nullptr)
{
tree *currentptr=new tree();
currentptr->value=value;
currentptr->left=nullptr;
currentptr->right=nullptr;
ptr=currentptr;
}
else
{
if (ptr->value>value)
{
addTree(ptr->left,value);
}
else
{
addTree(ptr->right,value);
}
}
}
void outtree(tree *ptr)
{
if (ptr==nullptr)
{
return;
}
deque<tree *> ktree;
ktree.push_back(ptr);
while (!ktree.empty())
{
tree *node=ktree.front();
ktree.pop_front();
cout<<node->value<<endl;
if (node->left)
{
ktree.push_back(node->left);
}
if (node->right)
{
ktree.push_back(node->right);
}
}
}
int main()
{
tree *root=nullptr;
addTree(root,8);
addTree(root,10);
addTree(root,6);
addTree(root,9);
addTree(root,11);
addTree(root,5);
addTree(root,7);
outtree(root);
return 0;
}