Xmas Code

Free a tree into a freelist linked by left node, without recursion:

freetree(t)
struct node *t;
{
        struct node **p,*sv;
        sv=freelist; freelist=0; p=&freelist;
        for(*p=t; *p; p=&p[0]->left);
        while(t) {
                for(*p=t->right; *p; p=&p[0]->left);
                t=t->left;
        }
        *p=sv;
}