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程式語言 - LeetCode - CPP - 606. Construct String from Binary Tree

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題目：


解答：

/**
 * 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:
    string tree2str(TreeNode* root) {
        if (!root) {
            return "";
        }

        string ans = to_string(root->val);

        if (root->left || root->right) {
            ans += "(" + tree2str(root->left) + ")";
        }

        if (root->right) {
            ans += "(" + tree2str(root->right) + ")";
        }

        return ans;
    }
};