Last active
October 9, 2017 19:12
-
-
Save Arnauld/00c7ed63257a1e18131e0bdf6d2fc451 to your computer and use it in GitHub Desktop.
Tree traversal with tail call recursion
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
-module(tree). | |
-export([main/0]). | |
-record(node, { | |
value = nil, | |
left = nil, | |
right = nil}). | |
% | |
% tc_pre_order | |
% | |
tc_pre_order(Fn, Node) -> | |
tc_pre_order(Fn, [Node], nil). | |
tc_pre_order(_, [], nil) -> | |
ok; | |
tc_pre_order(Fn, [X | Xs], nil) -> | |
tc_pre_order(Fn, Xs, X); | |
tc_pre_order(Fn, Xs, #node{value = V, left = L, right = R}) -> | |
Fn(V), | |
tc_pre_order(Fn, [R | Xs], L). | |
% | |
% tc_in_order | |
% | |
tc_in_order(Fn, Node) -> | |
tc_in_order0(Fn, [{node, Node}]). | |
tc_in_order0(__, []) -> | |
ok; | |
tc_in_order0(Fn, [{node, nil} | XS]) -> | |
tc_in_order0(Fn, XS); | |
tc_in_order0(Fn, [{node, N} | XS]) -> | |
#node{value = V, left = L, right = R} = N, | |
tc_in_order0(Fn, [{node, L}, {value, V}, {node, R} | XS]); | |
tc_in_order0(Fn, [{value, V} | XS]) -> | |
Fn(V), | |
tc_in_order0(Fn, XS). | |
% | |
%inorder traverse the tree and take Fn as a function to print each node | |
% | |
in_order(_, nil) -> | |
ok; | |
in_order(Fn, #node{value = V, left = L, right = R}) -> | |
in_order(Fn, L), | |
Fn(V), | |
in_order(Fn, R). | |
% | |
%preorder traverse the tree and take Fn as a function to print each node | |
% | |
pre_order(_, nil) -> | |
ok; | |
pre_order(Fn, {node, V, L, R}) -> | |
Fn(V), | |
pre_order(Fn, L), | |
pre_order(Fn, R). | |
% | |
% recursive insert to build the tree | |
% | |
insert(ND = #node{value = N, left = L}, V) when N > V -> | |
ND#node{left = insert(L, V)}; | |
insert(ND = #node{right = R}, V) -> | |
ND#node{right = insert(R, V)}; | |
insert(nil, V) -> | |
#node{value = V}. | |
main() -> | |
% | |
% build the tree using recursive insert function | |
% | |
TS = | |
[insert(insert(insert(insert(insert(insert(insert(insert(nil, 1), 2), 4), 7), 5), 6), 8), 9), | |
#node{value = 1, | |
left = #node{value = 2}, | |
right = #node{value = 3, | |
left = #node{value = 4}, | |
right = #node{value = 5, | |
right = #node{value = 6}}}}], | |
lists:foreach(fun eval_tree/1, TS). | |
eval_tree(T) -> | |
io:format("Tree is ~p~n", [T]), | |
F = fun(X) -> io:format("~p ", [X]) end, | |
% | |
%traverse the tree | |
% | |
io:format("~nTree traverse pre-order~n"), | |
pre_order(F, T), | |
io:format("~nTree traverse (tc)pre-order~n"), | |
tc_pre_order(F, T), | |
io:format("~nTree traverse in-order~n"), | |
in_order(F, T), | |
io:format("~nTree traverse (tc)in-order~n"), | |
tc_in_order(F, T), | |
io:format("~n--END--~n"). |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
see for original traversal :
https://github.com/jinchenbravo/Tree-traversal/blob/master/mcd.erl