二叉树的层序遍历（递归和非递归）

二叉树的定义

typedef struct node{

struct node *left, *right;

int val;

}Node, *BinTree;

非递归实现二叉树的层序遍历：

void PrintTree(BinTree root)

{

if(!root)

return;

queue q;

q.push(root);

BinTree p = root;

while(!q.empty())

{

p = q.front();

cout<val<<" ";

q.pop();

if(p->left)

q.push(p->left)

if(p->right)

q.push(p->right)

}

}

非递归实现二叉树的层序遍历且每层各占一行：

void PrintTreeLevel(BinTree root)

{

if(root == NULL)

return;

vector vec;

vec.push_back(root);

int cur = 0;

int last = 1;

while(cur < vec.size())

{

last = vec.size();

while(cur < last)//为了分层输出

{

cout<val<<" ";

if(vec[cur]->left != NULL)

vec.push_back(vec[cur]->left);

if(vec[cur]0>right != NULL)

vec.push_back(vec[cur]->right);

cur++;

}

cout<

}

}

递归实现二叉树的层序遍历：

class Solution {

public:

vector> levelorder(BinTree root)

{

vector> result;

level(result, root, 1);

return result;

}

}

void level(vector> &result, BinTree root, int num)

{

if(root ==NULL)

return;

if(num > result.size())

result.push_back(vector());

result[num - 1].push_back(root->val);

level(result, root->left, num+1);

level(result, root->right. num+1);

}