/**

  * 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)

     {

         int res = ;

         solute(root, res, false);

         return res;

     }

     void solute(TreeNode *root, int &sum, bool flag)

     {

         if(root == nullptr)

             return;

         if(!root->left && !root->right)

         {

             if(flag == true)

                 sum += root->val;

             return;

         }

         solute(root->left, sum, true);

         solute(root->right, sum, false);

         return;

     }

 };