Code

vector<vector<int>> pathsum(TreeNode* root, int val, int targetsum, vector<int> &current, vector<vector<int>> &ans) {
    if (root == nullptr) return ans;

    val += root->val;
    current.push_back(root->val);

    if (root->left == nullptr && root->right == nullptr && targetsum == val) {
        ans.push_back(current);
    } else {
        pathsum(root->left, val, targetsum, current, ans);
        pathsum(root->right, val, targetsum, current, ans);
    }

    current.pop_back(); // Backtrack
    return ans;
}

vector<vector<int>> Solution::pathSum(TreeNode* A, int B) {
    vector<vector<int>> ans;
    vector<int> current;
    pathsum(A, 0, B, current, ans);
    return ans;
}