Editing Iterative deepening depth-first search (section)

== Algorithm for directed graphs==
The following pseudocode shows IDDFS implemented in terms of a recursive depth-limited DFS (called DLS) for [[directed graph]]s. This implementation of IDDFS does not account for already-visited nodes.

 '''function''' IDDFS(root) '''is'''
     '''for''' depth '''from''' 0 '''to''' ∞ '''do'''
         found, remaining ← DLS(root, depth)
         '''if''' found ≠ '''null''' '''then'''
             '''return''' found
         '''else if''' not remaining '''then'''
             '''return''' '''null'''
 
 '''function''' DLS(node, depth) '''is'''
     '''if''' depth = 0 '''then'''
         '''if''' node is a goal '''then'''
             '''return''' (node, '''true''')
         '''else'''
             '''return''' ('''null''', '''true''')    ''(Not found, but may have children)''
 
     '''else if''' depth > 0 '''then'''
         any_remaining ← '''false'''
         '''foreach''' child '''of''' node '''do'''
             found, remaining ← DLS(child, depth−1)
             '''if''' found ≠ null '''then'''
                 '''return''' (found, '''true''')   
             '''if''' remaining '''then'''
                 any_remaining ← true    ''(At least one node found at depth, let IDDFS deepen)''
         '''return''' ('''null''', any_remaining)

If the goal node is found by '''DLS''', '''IDDFS''' will return it without looking deeper. Otherwise, if at least one node exists at that level of depth, the ''remaining'' flag will let '''IDDFS''' continue.

[[Tuple|2-tuples]] are useful as return value to signal '''IDDFS''' to continue deepening or stop, in case tree depth and goal membership are unknown ''a priori''. Another solution could use [[sentinel value]]s instead to represent ''not found'' or ''remaining level'' results.