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:
    vector<vector<int> > ans;
    void pre(TreeNode* root,vector<int> &temp){
        if(root == NULL)
            return;
        temp.push_back(root->val);
        pre(root->left,temp);
        pre(root->right,temp);
    }
    void Mid(TreeNode* root,vector<int> &temp){
        if(root == NULL)
            return;
        Mid(root->left,temp);
        temp.push_back(root->val);
        Mid(root->right,temp);
    }
    void End(TreeNode* root,vector<int> &temp){
        if(root == NULL)
            return;
        End(root->left,temp);
        End(root->right,temp);
        temp.push_back(root->val);
    }
    vector<vector<int> > threeOrders(TreeNode* root) {
        // write code here
        vector<int> temp;
        pre(root,temp);
        ans.push_back(temp);
        temp.clear();
        Mid(root,temp);
        ans.push_back(temp);
        temp.clear();
        End(root,temp);
        ans.push_back(temp);
        return ans;
    }
};