计算给定二叉树的所有左叶子之和。
示例:
3
/ \
9 20
/ \
15 7
在这个二叉树中,有两个左叶子,分别是 9 和 15,所以返回 24
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int sumOfLeftLeaves(TreeNode* root) {
if (root == NULL)
return 0;
if (root->left == NULL)
return sumOfLeftLeaves(root->right);
int sum = sumOfLeftLeaves(root->left) + sumOfLeftLeaves(root->right);
if (root->left->left == NULL && root->left->right == NULL)
sum += root->left->val;
return sum;
}
};