二叉树递归题目（一）

玖剹2025-11-14 19:09

一：计算布尔二叉树的值

1.1题目

题目链接：https://leetcode.cn/problems/evaluate-boolean-binary-tree/description/

1.2算法原理

1.3代码

cpp 复制代码

class Solution {
public:
    bool evaluateTree(TreeNode* root) 
    {
        if(root->right == nullptr)
            return root->val;

        bool leftval = evaluateTree(root->left);
        bool rightval = evaluateTree(root->right);

        return root->val == 2 ?  rightval | leftval : rightval & leftval;
    }
};

二：求根节点到叶节点数字之和

2.1题目

题目链接：https://leetcode.cn/problems/sum-root-to-leaf-numbers/description/

2.2算法原理

2.3代码

cpp 复制代码

class Solution {
public:
    int sumNumbers(TreeNode* root) {
        return dfs(root,0);
    }

    int dfs(TreeNode* root,int presum)
    {
        int sum = presum * 10+ root->val;

        if(root->left == nullptr && root->right == nullptr)
            return sum;
        
        int leftsum = 0, rightsum = 0;
        if(root->left)
            leftsum = dfs(root->left,sum);
        if(root->right)
            rightsum = dfs(root->right,sum);

        return leftsum + rightsum;
    }
};

三：二叉树剪枝

3.1题目

题目链接：https://leetcode.cn/problems/binary-tree-pruning/

3.2算法原理

3.3代码实现

cpp 复制代码

class Solution {
public:
    TreeNode* pruneTree(TreeNode* root) 
    {
        if(root == nullptr)
            return nullptr;

        root->left =  pruneTree(root->left);
        root->right = pruneTree(root->right);

        if(root->val == 0 && root->left == nullptr && root->right == nullptr)
        {
            //delete root;//内存泄漏，但是如果节点不是new出来的delete会报错
            root = nullptr;
        }
        return root;  
    }
};