层次遍历二叉树

1.层次遍历二叉树：

从上往下的层次遍历：

struct TreeNode

{

int val;

TreeNode*pleft;

TreeNode*pright;

}

void PrintNodeatLevel(TreeNode *root,int level)

{

if(!root)

{

return;

}

vector<TreeNode *>vec;

vec.push_back(root);

int cur=0;

int last;

while(cur<vec.size())

{

last=vec.size();

while(cur<last)

{

cout<<vec[cur]->val<<' ';

vec.push_back(root->left);

vec.push_back(root->right);

cur++;

}

cout<<endl;

}

}

 

采用栈的写法：

void printTopDown(BinaryTree* root)

{

deque<BinaryTree> dequeB;

deque.push_back(root);

while(!deque.empty())

{

BinaryTree*p=deque.front();

cout<<p->value<<endl;

if(p->left)

dequeB.push_back(p->left);

if(p->right)

dequeB.push_back(p->right);

}

}

从下往上访问：