[leetcode] Binary Tree Inorder Traversal

Binary Tree Inorder Traversal

使用递归

class Solution {private:    vector<int> res;public:    vector<int> inorderTraversal(TreeNode *root) {        if (root!=NULL) {            inorderTraversal(root->left);            res.push_back(root->val);            inorderTraversal(root->right);        }        return res;    }};

非递归，使用栈模拟

#include <iostream>#include <vector>#include <stack>#include <list>#include <queue>using namespace std;/** * Definition for binary tree */struct TreeNode {    int val;    TreeNode *left;    TreeNode *right;    TreeNode(int x) : val(x), left(NULL), right(NULL) {}};class Solution {private:    vector<int> res;    stack<TreeNode*> stk;public:    vector<int> inorderTraversal(TreeNode *root) {        if (root==NULL) {            return res;        }        stk.push(root);        while (!stk.empty()) {            TreeNode *tmp=stk.top();            if (tmp->left==NULL&&tmp->right==NULL) {                stk.pop();                res.push_back(tmp->val);            }else{                stk.pop();//通用模板，调整入栈顺序，即可实现先序、中序、后序遍历                if (tmp->right!=NULL) {                    stk.push(tmp->right);                }                stk.push(tmp);                if (tmp->left!=NULL) {                    stk.push(tmp->left);                }                tmp->left=tmp->right=NULL;            }                    }        return res;    }};

参考：

Binary Tree Inorder Traversal