题解 | #二叉搜索树的第k个节点#

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
#include <algorithm>
#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 proot TreeNode类 
     * @param k int整型 
     * @return int整型
     */
    static bool compare_treenode(TreeNode* a , TreeNode* b){
        return a->val<b->val;
    }
    vector<TreeNode*>reaper_vec;
    int KthNode(TreeNode* proot, int k) {
        // write code here
        if (!proot || k==0) {
            return -1;
        }
        reaper_allNodes(proot);
        if (k>reaper_vec.size()) {
            return -1;
        }
        sort(reaper_vec.begin(), reaper_vec.end(),compare_treenode);
        return reaper_vec[k-1]->val;
    }
    //前序法遍历树
    void reaper_allNodes(TreeNode* proot){
        if (!proot) {
            return;
        }
        reaper_vec.push_back(proot);
        reaper_allNodes(proot->left);
        reaper_allNodes(proot->right);
    }
};