Kth-Smallest-Element-in-a-BST

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题目地址

LeetCode#230 Kth Smallest Element in a BST

题目描述

  Given a binary search tree, write a function kthSmallest to find the kth smallest element in it.

Note:
  You may assume k is always valid, 1 ≤ k ≤ BST’s total elements.

Follow up:
  What if the BST is modified (insert/delete operations) often and you need to find the kth smallest frequently? How would you optimize the kthSmallest routine?

解题思路

  题目要求找到树种第K个最小的值，可以将树的节点值保存到容器数组中，然后排序就可以了。emm

解题代码【.CPP】

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/**
 * 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 {
    void getValue(TreeNode* root , vector<int>& values){
        if(!root) return;
        values.push_back(root->val);
        getValue(root->left , values);
        getValue(root->right , values);
    }

public:
    int kthSmallest(TreeNode* root, int k) {
        vector<int> valuse(0);
        getValue(root , valuse);
        sort(valuse.begin(),valuse.end());
        return valuse[k-1];
    }
};
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