Hamiltonian Paths in C-shaped Grid Graphs
  We study the Hamiltonian path problem in C-shaped grid graphs, and present the necessary and sufficient conditions for the existence of a Hamiltonian path between two given vertices in these graphs. We also give a linear-time algorithm for finding a Hamiltonian path between two given vertices of a C-shaped grid graph, if it exists. 
Fatemeh Keshavarz-Kohjerdi and Alireza Bagheri
cs.CC