In this paper, we propose an approach to construction of polar codes for successive cancellation list (SCL) decoding with a preset list size. For a given code length, we construct a trellis through which a path corresponds to a polar code. Then, we employ a sequential search algorithm to find an expected path based on four path metrics and five path selection rules. Additionally, for polarization-adjusted convolutional (PAC) construction, we optimize the convolutional generator polynomial based on our constructed polar code. Numerical results show that our polar/PAC codes can achieve satisfactory performance.