题解 | #实现二叉树先序，中序和后序遍历#

简单粗暴实现：三个方法都遍历一下即可

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */

class Solution {
public:
    /**
     * 
     * @param root TreeNode类 the root of binary tree
     * @return int整型vector<vector<>>
     */
    void front(TreeNode* Node, vector<int> &f){
        if(!Node) return;
        f.push_back(Node->val);
        front(Node->left, f);
        front(Node->right, f);
    }
    void mid(TreeNode* Node, vector<int> &m){
        if(!Node) return;
        mid(Node->left, m);
        m.push_back(Node->val);
        mid(Node->right, m);
    }
    void back(TreeNode* Node, vector<int> &b){
        if(!Node) return;
        back(Node->left, b);
        back(Node->right, b);
        b.push_back(Node->val);
    }
    
    vector<vector<int> > threeOrders(TreeNode* root) {
        // write code here
        vector<int> f, m, b;
        vector<vector<int>> all;
        front(root, f);
        mid(root, m);
        back(root, b);
        all.push_back(f);
        all.push_back(m);
        all.push_back(b);
        return all;
    }
};