404. Sum of Left Leaves

// we could also use breadth-first search(iteration or level search)

class Solution 
{
private:
    int result = 0;
    
    void sumOfLeftLeaves(TreeNode *i_root, int isLeftChild)
    {
        if(!i_root->left && !i_root->right) result += i_root->val * isLeftChild;
        
        if(i_root->left) sumOfLeftLeaves(i_root->left, 1);
        if(i_root->right) sumOfLeftLeaves(i_root->right, 0);
    }
public:
    // int sumOfLeftLeaves(TreeNode* root)
    int sumOfLeftLeaves(TreeNode *i_root) 
    {
        if(!i_root) return result;
        
        sumOfLeftLeaves(i_root, 0);
        
        return result;
    }
};