An apparatus that receives a non-binary polar code through a channel includes a low-complexity decoder and a memory. The low-complexity decoder is configured to selectively calculate first common terms for input symbols in the non-binary polar code other than a first input symbol corresponding to a first target output symbol. The selective calculation uses a lower triangular kernel and log likelihood ratios of the input symbols generated based on a channel characteristic of the channel. The low-complexity decoder is also configured to calculate log likelihood ratios of the first target output symbol using the first common terms and to determine a value of the first target output symbol based on the log likelihood ratios of the first target output symbol. The memory is accessible by the low-complexity decoder and is configured to store the first common terms.