[leetcode]94-二叉树的中序遍历

/**
 * 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> inorderTraversal(TreeNode* root) {
        vector<int> v;
        stack<TreeNode *> st;
        TreeNode *p;
        p = root;
        while (p || !st.empty()) {
            // 循环遍历左子树
            while (p) {
                st.push(p);
                p = p->left;
            }

            if (!st.empty()) {
                // 弹出栈顶节点
                p = st.top();
                st.pop();
                // 访问节点
                v.push_back(p->val);
                // 访问右子树
                p = p->right;
            }
        }
        return v;
    }
};

/**

* 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> inorderTraversal(TreeNode* root) {

vector<int> v;

stack<TreeNode *> st;

TreeNode *p;

p = root;

while (p || !st.empty()) {

// 循环遍历左子树

while (p) {

st.push(p);

p = p->left;

}

if (!st.empty()) {

// 弹出栈顶节点

p = st.top();

st.pop();

// 访问节点

v.push_back(p->val);

// 访问右子树

p = p->right;

}

return v;

}

};

[leetcode]94-二叉树的中序遍历

3.2 递归代码

/**
 * 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 {
private:
    void inorderTraversal(TreeNode *root, vector<int> &v) {
        if (root == nullptr) {
            return ;
        }
        if (root->left) {
            inorderTraversal(root->left, v);
        }
        v.push_back(root->val);
        if (root->right) {
            inorderTraversal(root->right, v);
        }
    }
public:
    vector<int> inorderTraversal(TreeNode* root) {
        vector<int> v;
        inorderTraversal(root, v);
        return v;
    }
};