In this paper, a HPSIL for solving the FCTP has been proposed. To investigate the influence of the parameters on the performance of the algorithm, experimental designs have been carried out. In the proposed HPSIL algorithm a flexible particle structure combined with decoding and allocation procedures are used instead of a Prüfer number and a spanning tree used with a genetic algorithm. One of the major contributions is that the HPSIL generates the feasibility of all generated solutions and can be used for solving both balanced and unbalanced FCTPs.