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• NC45 实现二叉树先序，中序和后序遍历

NC45 实现二叉树先序，中序和后序遍历

题目描述
分别按照二叉树先序，中序和后序打印所有的节点。
示例1
输入
{1,2,3}
返回值
[[1,2,3],[2,1,3],[2,3,1]]

/**
 * 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<>>
     */
    vector<int> pre;
    vector<int> in;
    vector<int> post;
    vector<vector<int> > threeOrders(TreeNode* root) {
        // write code here
        if(root==NULL)
            return vector<vector<int>>{pre,in,post};
        preOrder(root);
        inOrder(root);
        postOrder(root);
        vector<vector<int>> ans;
        ans.push_back(pre);
        ans.push_back(in);
        ans.push_back(post);
        return ans;
    }
    void preOrder(TreeNode* root) {
        if (root == NULL) return;
        pre.push_back(root->val);
        preOrder(root->left);
        preOrder(root->right);
    }
     
    void inOrder(TreeNode* root) {
        if (root == NULL) return;
        inOrder(root->left);
        in.push_back(root->val);
        inOrder(root->right);
    }
     
    void postOrder(TreeNode* root) {
        if (root == NULL) return;
        postOrder(root->left);
        postOrder(root->right);
        post.push_back(root->val);
    }
};