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) {}
 * };
 */
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 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;
        if (root == NULL)
        {
            return ans;
        }
        vector<pair<double,int>> diffValue;
        //采用深度优先搜索
        stack<TreeNode* > st;
        st.push(root);
        while(!st.empty())
        {
            TreeNode* Node = st.top();
            st.pop();
            if (Node != NULL)
            {
                if (Node->right != NULL)
                {
                    st.push(Node->right);
                }
                if (Node->left != NULL)
                {
                    st.push(Node->left);
                }
                st.push(Node);
                st.push(NULL);
            }
            else
            {
                Node = st.top();
                st.pop();
                diffValue.emplace_back(abs(Node->val - target),Node->val);
            }
        }
        sort(diffValue.begin(),diffValue.end(),[](const pair<double,int> a,const pair<double,int> b)
        {
            return a.first < b.first;
        });
        // for (auto it : diffValue)
        // {
        //     cout << it.second << " " << it.first << endl;
        // }
        for (int i = 0; i < m;++i)
        {
            ans.push_back(diffValue[i].second);
        }
        sort(ans.begin(),ans.end());
        return ans;
    }
};