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The MIT License (MIT)

Copyright © 2022-2023 Lumynous

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

題目連結: Leetcode

題目概要

給一正整數 n 回傳所有有剛好n個節點的可能的完整二元樹

想法

遞迴DP

在節點數為i個時, 完整二分樹的所有可能狀況可由i-2個節點的二分樹得知
因此建表紀錄在j個節點時的完整二分樹的所有可能狀況
再遞迴出i個節點的二分樹所有可能狀況

參考解法

歡迎補充

CPP 遞迴DP

class Solution {
public:
    vector<TreeNode*> ans;  
    unordered_map<int, vector<TreeNode*>> table;
    vector<TreeNode*> createTree(int n){
        if (table.find(n) != table.end()){
            return table[n];
        }
        vector<TreeNode*> temp;
        for (int i = 1; i < n; i+=2){
            vector<TreeNode*> left = createTree(i);
            vector<TreeNode*> right = createTree(n-i-1);
            for (auto l: left){
                for (auto r: right){
                    TreeNode* root = new TreeNode(0, l, r);
                    temp.push_back(root);
                }
            }
        }
        table.insert({n, temp});
        return temp;
    }

    vector<TreeNode*> allPossibleFBT(int n) {
        if (!(n%2)) return {};
        if (n == 1) return {new TreeNode()};
        vector<TreeNode*> temp = {new TreeNode()};
        table.insert({1, temp});
        return createTree(n);
    }
};

---

Dark Theme License

The MIT License (MIT)

Copyright © 2022 Luminous-Coder

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.