题意
思路
直接统计
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) {
if (root == NULL)
return 0;
int sum = 0;
sum += sumOfLeftLeaves(root->left);
sum += sumOfLeftLeaves(root->right);
if (root->left != NULL && root->left->left == NULL && root->left->right == NULL)
sum += root->left->val;
return sum;
}
};