left leaf求和,按照定义dfs即可
C++ 代码
/**
* 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:
int sumOfLeftLeaves(TreeNode* root) {
dfs(root);
return res_;
}
void dfs(TreeNode* root) {
if(!root)return;
if(root->left && !root->left->left && !root->left->right)res_ += root->left->val;
dfs(root->left);
dfs(root->right);
}
private:
int res_ = 0;
};