358. 트리 순회 함수와 방문 순번

1if undefined for f
2 
3undefined und
4    for unde
5    undefined undefine
6    undefined undefined
7un
8 
9{ undefined undefined int i
10    undefined } for (a) u
11    undefined
12    { for print undefined } 
13    0; i undefined unde
14    { undefined 0; undef
15    undefine
16    undefined (a) undefined = undefi
17    undefined undefined undefined 
18i
19 
20undefined (a) un
21    undefined i undefined (a) undefi
22    undefined { undefined undefined 
23    x x print x undefined undefi
24    print undefined if if x if undef
25    undefined undefined undefine
26    undefined undefined un
27    undefined undefined und
28    for if undefined undefined undefine
29    undefined
30u