8-queens problem can be solved by
START
1. begin from the leftmost column
2. if all the queens are placed,
return true/ print configuration
3. check for all rows in the current column
a) if queen placed safely, mark row and column; and
recursively check if we approach in the current
configuration, do we obtain a solution or not
b) if placing yields a solution, return true
c) if placing does not yield a solution, unmark and
try other rows
4. if all rows tried and solution not obtained, return
false and backtrack
END