404. Sum of Left Leaves

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// 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;
    }
};