//404

Find the sum of all left leaves in a given binary tree.

Example:

3
/
9 20
/
15 7

There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.

class Solution {
public:
    int sumOfLeftLeaves(TreeNode* root) {
        if(root==NULL){
            return 0;
        }

        //left leaf,recursion root->right
        if(root->left && !root->left->left && !root->left->right){
            return root->left->val+sumOfLeftLeaves(root->right);
        }

        return sumOfLeftLeaves(root->left)+sumOfLeftLeaves(root->right);
    }
};