二叉樹的定義

typedef struct node{

struct node *left, *right;

int val;

}Node, *BinTree;

非遞迴實現二叉樹的層序遍歷：

void PrintTree(BinTree root)

{

if(!root)

return;

queue<Node *> q;

q.push(root);

BinTree p = root;

while(!q.empty())

{

p = q.front();

cout<<p->val<<" ";

q.pop();

if(p->left)

q.push(p->left)

if(p->right)

q.push(p->right)

}

}

非遞迴實現二叉樹的層序遍歷且每層各佔一行：

void PrintTreeLevel(BinTree root)

{

if(root == NULL)

return;

vector<Node *> vec;

vec.push_back(root);

int cur = 0;

int last = 1;

while(cur < vec.size())

{

last = vec.size();

while(cur < last)//為了分層輸出

{

cout<<vec[cur]->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<<endl;

}

}

遞迴實現二叉樹的層序遍歷：

class Solution {

public:

vector<vector<int>> levelorder(BinTree root)

{

vector<vector<int>> result;

level(result, root, 1);

return result;

}

}

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

{

if(root ==NULL)

return;

if(num > result.size())

result.push_back(vector<int>());

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

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

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

}