leetcode算法题--根据描述创建二叉树

原题链接：https://leetcode.cn/problems/create-binary-tree-from-descriptions/

class Solution {
public:
    TreeNode* createBinaryTree(vector>& descriptions) {
        unordered_map mp;
        unordered_map isRoot;
        for (auto desc : descriptions) {
            int p = desc[0], c = desc[1];
            if (!mp.count(p)) {
                mp[p] = new TreeNode(p);
            }
            if (!mp.count(c)) {
                mp[c] = new TreeNode(c);
            }
            if (!isRoot.count(p)) {
                isRoot[p] = true;
            }
            isRoot[c] = false;
            TreeNode* node = mp[p];
            TreeNode* child = mp[c];
            if (desc[2]) {
                node->left = child;
            } else {
                node->right = child;
            }
        }
        for (auto [k, v] : isRoot) {
            if (v) return mp[k];
        }
        return NULL;  
    }
};