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;
 * };
 */

class Solution {
public:
    /**
     * 
     * @param root TreeNode类 the root of binary tree
     * @return int整型vector<vector<>>
     */
     void threeOrders(TreeNode* root, vector<vector<int> > &vect){
        if(!root)
            return;
        vect[0].push_back(root->val);
        threeOrders(root->left,vect);
        vect[1].push_back(root->val);
        threeOrders(root->right,vect);
        vect[2].push_back(root->val);
    }
    vector<vector<int> > threeOrders(TreeNode* root) {
        vector<vector<int> > vect;
        vect.resize(3);
        threeOrders(root,vect);
        return vect;
    }
};