Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Computer Science

First Advisor

S. S. Iyengar


This dissertation presents new heuristic search algorithms, the Guided Minimum Detour (GMD) algorithm and the Line-by-Line Guided Minimum Detour (LGMD) algorithm for searching rectilinear ($L\sb1$) shortest paths in the presence of rectilinear obstacles. The GMD algorithm combines the best features of maze-running algorithms and line-search algorithms. The LGMD algorithm is a modification of the GMD algorithm that improves on efficiency using line-by-line extensions. Our GMD and LGMD algorithms always find a rectilinear shortest path using the guided $A\sp*$ search method without constructing a connection graph that contains a shortest path. The GMD algorithm and the LGMD algorithm can be implemented in $O(m + (e + N$)loge) and $O((e + N$)loge) time, respectively, and $O(e + N$) space, where m is the total number of searched nodes, e is the number of boundary sides of obstacles, and N is the total number of searched line segments. We consider the problem of finding a shortest path in terms of the number of bends and the combined length and bends.