Binary Tree Inorder Traversal

最新推荐文章于 2019-05-08 20:18:00 发布

转载最新推荐文章于 2019-05-08 20:18:00 发布 · 80 阅读

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原文链接：http://www.cnblogs.com/kwill/archive/2013/06/06/3122809.html

文章标签：

#c/c++

本文介绍了一种不使用递归的方法来完成二叉树节点值的中序遍历。通过栈来辅助实现迭代过程，避免了递归带来的栈溢出风险。文章提供了一个具体的C++实现示例。

Given a binary tree, return the inorder traversal of its nodes' values.

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

return [1,3,2].

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

/**
 * 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> vt;
        if (!root){
            return vt;
        }
        
        std::stack<TreeNode *> stk;
        TreeNode * p = root;
        
        while(!stk.empty() || p){
            while(p){
                stk.push(p);
                p = p->left;
            }
            if (!stk.empty()){
                TreeNode * q = stk.top();
                stk.pop();
                
                vt.push_back(q->val);
                if (q->right){
                    p = q->right;
                }else{
                    p = NULL;
                }   
            }
        }
        
        return vt;
    }
};