剑指offer--面试题23：从上往下打印二叉树

题目描述

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    # 返回从上到下每个节点值列表，例：[1,2,3]
    def PrintFromTopToBottom(self, root):
        # write code here
        if root is None:
            return []
        from collections import deque
        queue = deque([root])
        #curLevel = 1
        result = []
        while queue:
            front = queue.popleft()#队头
            #curLevel -= 1
            result.append(front.val)
            if front.left:
                queue.append(front.left)
            if front.right:
                queue.append(front.right)
            #if curLevel==0:
            #    curLevel = len(queue)
        return result

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/
class Solution {
public:
    vector<int> PrintFromTopToBottom(TreeNode *root) {
        vector<int> result;
        if(root==NULL)
            return result;
        queue<TreeNode *> q;
        q.push(root);
        while(!q.empty()){
            TreeNode *front = q.front();
            q.pop();
            result.push_back(front->val);
            if(front->left)
                q.push(front->left);
            if(front->right)
                q.push(front->right);
        }
        return result;
    }
};