LeetCode 230 Kth Smallest Element in a BST

题目链接：点击这里

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void inorder(TreeNode* r, vector<int>& v)
    {
        if(r!=NULL)
        {
            inorder(r->left, v);
            v.push_back(r->val);
            inorder(r->right, v);
        }
    }

    int kthSmallest(TreeNode* root, int k) {
        vector<int> v;
        inorder(root, v);
        return v[k-1];
    }
};