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#include<stdio.h>
#include<stdlib.h>
#include<utility>
struct tree {
tree(int e, tree* l, tree *r) : element(e), left(l), right(r) {}
int element;
tree *left;
tree *right;
};
enum DIR { LEFT_CHILD, RIGHT_CHILD };
struct stack {
stack(DIR d, tree *v, stack *p) : dir(d), val(v), parent(p) {}
DIR dir;
tree *val;
stack *parent;
};
std::pair<DIR, tree*> pop(stack*& s) {
auto res = std::make_pair(s->dir, s->val);
stack *tmp = s;
s = s->parent;
delete tmp;
return res;
}
void push(DIR dir, tree *t, stack*& s) {
s = new stack(dir, t, s);
}
void print_tree(tree *t) {
tree *cur = t;
stack *s = NULL;
begin_print_node:
if (cur == NULL) {
goto dispatch_stack_frame;
} else {
printf("(");
push(LEFT_CHILD, cur, s);
cur = cur->left;
goto begin_print_node;
}
print_element:
printf(" %d ", cur->element);
push(RIGHT_CHILD, cur, s);
cur = cur->right;
goto begin_print_node;
finish_print_node:
printf(")");
goto dispatch_stack_frame;
dispatch_stack_frame:
std::pair<DIR, tree*> top_frame;
if (s == NULL) goto end;
top_frame = pop(s);
cur = top_frame.second;
if (top_frame.first == LEFT_CHILD) goto print_element;
else goto finish_print_node;
end:
return;
}
int main() {
tree *a = new tree(1, NULL, NULL);
tree *b = new tree(2, NULL, a);
tree *c = new tree(3, a, b);
print_tree(c);
return 0;
}
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