[leetcode]404. Sum of Left Leaves

404. Sum of Left Leaves

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

Example:

    3   / \  9  20    /  \   15   7There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.

    int sumOfLeftLeaves(TreeNode* root) {        if( root == nullptr ) return 0;                if( root->left == nullptr && root->right == nullptr ) return 0;                if( root->left != nullptr && root->left->left == nullptr && root->left->right == nullptr )             return root->left->val + sumOfLeftLeaves( root->right );        return sumOfLeftLeaves( root->left ) + sumOfLeftLeaves( root->right );    }