LeetCode 1022 从根到叶的二进制数之和[dfs] HERODING的LeetCode之路

Posted 2022-06-01 HERODING23

解题思路：
非常简单的一道dfs题目，从上到下不断记录当前路径的数值，直到叶子节点更新ans，代码如下：

/**
 * 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 
private:
    int ans = 0;
public:
    int sumRootToLeaf(TreeNode* root) 
        if(root == nullptr) return 0;
        dfs(root, 0);
        return ans;
    
    
    void dfs(TreeNode* node, int num) 
        if(node == nullptr) return;
        num = (num << 1) + node->val;
        if(node->left == nullptr && node->right == nullptr) 
            ans += num;
        
        dfs(node->left, num);
        dfs(node->right, num);
    
;