1 /**
2 * Definition for a binary tree node.
3 * struct TreeNode {
4 * int val;
5 * TreeNode *left;
6 * TreeNode *right;
7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {}
8 * };
9 */
10 class Solution {
11 public:
12 int sumOfLeftLeaves(TreeNode* root) {
13 int res=0;
14 if(root==NULL) return res;
15 //单节点
16 if(!root->left && !root->right) return res;
17 //到达左叶子节点
18 if(root->left && !root->left->left && !root->left->right) res+= root->left->val;
19 else if(root->left) res+=sumOfLeftLeaves(root->left);
20 if(root->right) res+=sumOfLeftLeaves(root->right);
21 return res;
22 }
23 };
