165. 구조체 트리 후위 순회의 k번째 노드

1= undefined for un
2 
3} print x und
4    undefine
5    = undefined undefi
6    i (a) undefined for
70;
8 
9for undefine
10undefined undef
11 
12int } undefined i undefined undefi
13    undefined undefined } 
14    x undefined print
15    = if undefined i }
16    undefi
17    undefined print int for if { 
180
19 
20undefined un
21    undefined undefined x undefined 
22    undefined undefined (a) x undefi
23    } for i { undefined undefined 
24    undefined undefined undefined 
25    undefined undefined undefine
26    (a) print 0;
27    undefined undefined undefined 
28    undefined
29u