test30, Pascal - rextester

test30

program test29;
{pointer example of direct chain growth, key inf change and binary trees}
type tree=^top;
    top=record
            inf:char ;
            left, right:tree
            end ;
 var l:tree;

procedure sostavlenie2(var d:tree; element:char) ;{recursive procedure}
begin
    if d=Nil 
    then begin
          New(d) ;
          d^.inf:=element ;
          d^.left:=Nil ;
          d^.right:=Nil ;
          end
        else if element< d^.inf
           then sostavlenie2(d^.left,element)
           else sostavlenie2(d^.right,element)
end ;
function branch_search(d:tree;element:char):boolean ;{recursive function}
begin
   if d=Nil
      then branch_search:=false
      else if d^.inf=element
         then branch_search:=true
         else if element<d^.inf
           then branch_search:=branch_search(d^.left, element)
           else branch_search:=branch_search(d^.right, element)
  
 end;
 begin
  sostavlenie2(l, 'c') ;{enrich the binary tree with element 'a'}
  sostavlenie2(l, 'm') ;{enrich the binary tree with element 'b'}
  sostavlenie2(l, 'b') ;{enrich the binary tree with element 'c'}
  writeln(branch_search(l,'j'));{answer - does the element 'a' present in the binary tree? TRUE}
 end.


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