题解 | #牛牛的二叉树问题#

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
#include <set>
#include <utility>
using pii = pair<double, int>;
struct compare {
    bool operator() (pii p1, pii p2){
        return p1.first < p2.first;
    }
};
class Solution {

private: multiset<pii,compare> res;
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 root TreeNode类 
     * @param target double浮点型 
     * @param m int整型 
     * @return int整型vector
     */
    vector<int> findClosestElements(TreeNode* root, double target, int m) {
        // write code here
        vector<int> ans;
        preOrder(root,target);
        for(auto it = res.begin(); it != res.end() && m >0; it++, m--){
            ans.emplace_back(it->second);
        }
        sort(ans.begin(), ans.end());
        return ans;
    }
    void preOrder(TreeNode* root,double target){
        if (root == nullptr) {
            return;
        }
        res.insert({abs(root->val - target),root->val});
        preOrder(root->left,target);
        preOrder(root->right,target);
    }
};