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题目:
Given a binary tree, return the preorder traversal of its nodes’ values.
解释:
二叉树前序遍历。需要额外写一个函数。
python代码:
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def preorderTraversal(self, root):
"""
:type root: TreeNode
:rtype: List[int]
"""
#递归写法
result=[]
def pre(root,result):
if root==None:
return None
result.append(root.val)
pre(root.left,result)
pre(root.right,result)
pre(root,result)
return result
c++代码:
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<int> preorderTraversal(TreeNode* root) {
vector<int> result;
pre(root,result);
return result;
}
void pre(TreeNode* root ,vector<int>&result){
if(root)
{
result.push_back(root->val);
pre(root->left,result);
pre(root->right,result);
}
}
};
总结:
cpp,注意定义函数的时候形式参数是引用…cpp确实比python需要注意的地方多