Solving problems does not always proceed on a direct route to the
goal. Sometimes we make progress by pursuing one approach only to discover
that we are stuck because we took a wrong turn. In those cases, we
backtrack in our exploration and take a different turn at some branch, in
the hope that it leads us to a solution. Algorithms can proceed like
that. In the first subsection, we deal with an algorithm that can help us
traverse a graph, which is of course the situation we just discussed. The
second subsection is an extended exercise that uses backtracking in the
context of chess.