LCR 056. 两数之和 IV - 输入二叉搜索树

题意

题目链接

思路

代码

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    void tree2vetor(TreeNode *root, vector<int> &num) {
        if (root == NULL) {
            return ;
        }
        tree2vetor(root->left, num);
        num.push_back(root->val);
        tree2vetor(root->right, num);
    }
    bool findTarget(TreeNode* root, int k) {
        vector<int> num;
        tree2vetor(root, num);
        int l = 0, r = num.size() - 1 ;
        while (l < r)
        {
            const int tmp = num[l] + num[r];
            if (tmp == k)
                return true;
            if (tmp > k)
                r--;
            else 
                l++;
        }
        return false;
    }
};