题解 | #实现二叉树先序，中序和后序遍历#

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
#include <vector>
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 the root of binary tree
     * @return int整型vector<vector<>>
     */
    vector<vector<int> > threeOrders(TreeNode* root) {
        // write code here
        vector<vector<int> > v;
        vector<int> Tree1;
        vector<int> Tree2;
        vector<int> Tree3;
        preOrder(Tree1,root);
        inOrder(Tree2,root);
        postOrder(Tree3,root);
        v.push_back(Tree1);
        v.push_back(Tree2);
        v.push_back(Tree3);
        return v;
        
    }
    void preOrder(vector<int> &Tree,TreeNode *root){
        if(root == NULL){
            return;
        }
        Tree.push_back(root->val);
        preOrder(Tree, root->left);
        preOrder(Tree, root->right);
    }
        void inOrder(vector<int> &Tree,TreeNode *root){
        if(root == NULL){
            return;
        }
        inOrder(Tree, root->left);
        Tree.push_back(root->val);
        inOrder(Tree, root->right);
    }
        void postOrder(vector<int> &Tree,TreeNode *root){
        if(root == NULL){
            return;
        }
        postOrder(Tree, root->left);
        postOrder(Tree, root->right);
        Tree.push_back(root->val);
    }
};