Question

Implement the depth-first search (DFS) algorithm. To make your algorithm complete, write the graph search version of DFS, which avoids expanding any already visited states. Your code should quickly find a solution for tinyMaze.txt (below)

%%%%%%%
% S%
% %%% %
% % %
%% %%
%F %%%%
%%%%%%%

Answer 1

Assuming that we can move in all 8 directions:

The algorithm goes as follows:-

• From a cell u, run dfs(v) for all v belongs to neighbour of u if they are not visited. Also visit them before calling dfs. If solution is found, return the solution else set visited of v to be false and continue. If no solution is found, then return false.
• Note that if value of node is %, then return false.
• Note that if value of node is ' ' then only continue.
• Note that if the value is 'F' then return true.

Pseudo code:

dfs(i, j):

if val[i][j] == 'D' then return true

if val[i][j] == '%' then return false

for k,l in neighbours(i, j):

if visited[k][l] is false:

visited[k][l] = true

if dfs(k, l) is true then return true

visited[k][l] = false

return false

call dfs(x, y) where val[x][y] is 'S'

neighbours(i, j):

return list((i +- 0,1, j +- 0,1))

In case of any doubts, please ask in comments