【leetcode】Binary Tree Inorder Traversal

本文详细介绍了如何使用递归和迭代方法实现二叉树的中序遍历,并提供了相应的C/C++代码实现。通过实例演示了如何在不使用额外数据结构的情况下,仅使用栈进行迭代操作完成遍历过程。

摘要生成于 C知道 ,由 DeepSeek-R1 满血版支持, 前往体验 >

Question :

Given a binary tree, return theinordertraversal of its nodes' values.

For example:
Given binary tree{1,#,2,3},

   1
    \
     2
    /
   3

return[1,3,2].

Note:Recursive solution is trivial, could you do it iteratively?

confused what"{1,#,2,3}"means?> read more on how binary tree is serialized on OJ.


Anwser 1 :

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> inorderTraversal(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> result(0);
        
        if (root == NULL)  return result;
        
        stack<TreeNode *> S;
        TreeNode* p = root;
        
        do
        {
            if (p != NULL) {
                S.push(p);
                p = p->left;
            } else {
                p = S.top();
                S.pop();
                
                result.push_back(p->val);
                p = p->right;
            }
        }while(!S.empty() || p != NULL);
        
        return result;
    }
};


Anwser 2 :

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    
    void dfs(TreeNode *p, vector<int> &result)
    {
        if(p->left != NULL)
            dfs(p->left, result);
            
        result.push_back(p->val);
        
        if(p->right!=NULL)
            dfs(p->right, result);
    }
    
    vector<int> inorderTraversal(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        TreeNode * head = root;
        vector<int> result;
        result.clear();
        
        if(head!=NULL) {
            dfs(head, result);
        }
            
        return result;
    }
};



Anwser 3 :

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> inorderTraversal(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> result;
        result.clear();
        stack<TreeNode *> stack_in;
        stack<TreeNode *> stack_out;
        
        if(root == NULL) return result;
        
        stack_in.push(root);
        while(!stack_in.empty())
        {
            TreeNode *node_in = stack_in.top();
            stack_in.pop();
            stack_out.push(node_in);
            if(node_in->right!=NULL && node_in->left!=NULL)
            {
                stack_in.push(node_in->right);
                stack_in.push(node_in->left);
            } else if(node_in->left!=NULL && node_in->right==NULL) {
                    stack_in.push(node_in->left);
            } else if(node_in->left==NULL && node_in->right!=NULL) {
                    stack_in.push(node_in->right);
                    result.push_back(node_in->val);
                    stack_out.pop();
            } else {
                result.push_back(node_in->val);
                stack_out.pop();
                while(!stack_out.empty())
                {
                    TreeNode * tmp = stack_out.top();
                    stack_out.pop();
                    result.push_back(tmp->val);
                    if(tmp->right!=NULL)
                        break;
                }
            }
        }
        return result;
    }
};


参考推荐:

Binary Tree Inorder Traversal


评论
添加红包

请填写红包祝福语或标题

红包个数最小为10个

红包金额最低5元

当前余额3.43前往充值 >
需支付:10.00
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明:

1.余额是钱包充值的虚拟货币,按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载,可以购买VIP、付费专栏及课程。

余额充值