Editing Backtracking (section)

===Pseudocode===
In order to apply backtracking to a specific class of problems, one must provide the data ''P'' for the particular instance of the problem that is to be solved, and  six [[procedural parameter]]s, ''root'', ''reject'', ''accept'', ''first'', ''next'', and ''output''. These procedures should take the instance data ''P'' as a parameter and should do the following:
# ''root''(''P''):  return the partial candidate at the root of the search tree.
# ''reject''(''P'',''c''):  return ''true'' only if the partial candidate ''c'' is not worth completing.
# ''accept''(''P'',''c''): return ''true'' if ''c'' is a solution of ''P'', and ''false'' otherwise.
# ''first''(''P'',''c''): generate the first extension of candidate ''c''.
# ''next''(''P'',''s''): generate the next alternative extension of a candidate, after the extension ''s''.
# ''output''(''P'',''c''):  use the solution ''c'' of ''P'', as appropriate to the application.

The backtracking algorithm reduces the problem to the call ''backtrack''(''P'', ''root''(''P'')), where ''backtrack'' is the following recursive procedure:

 '''procedure''' backtrack(P, c) '''is'''
     '''if''' reject(P, c) '''then''' return
     '''if''' accept(P, c) '''then''' output(P, c)
     s ← first(P, c)
     '''while''' s ≠ NULL '''do'''
         backtrack(P, s)
         s ← next(P, s)