Task: Same fringe

C: #include <stdio.h>
#include <stdlib.h>
#include <ucontext.h>

typedef struct {
	ucontext_t caller, callee;
	char stack[8192];
	void *in, *out;
} co_t;

co_t * co_new(void(*f)(), void *data)
{
	co_t * c = malloc(sizeof(*c));
	getcontext(&c->callee);
	c->in = data;

	c->callee.uc_stack.ss_sp = c->stack;
	c->callee.uc_stack.ss_size = sizeof(c->stack);
	c->callee.uc_link = &c->caller;
	makecontext(&c->callee, f, 1, (int)c);

	return c;
}

void co_del(co_t *c)
{
	free(c);
}

inline void
co_yield(co_t *c, void *data)
{
	c->out = data;
	swapcontext(&c->callee, &c->caller);
}

inline void *
co_collect(co_t *c)
{
	c->out = 0;
	swapcontext(&c->caller, &c->callee);
	return c->out;
}



typedef struct node node;
struct node {
	int v;
	node *left, *right;
};

node *newnode(int v)
{
	node *n = malloc(sizeof(node));
	n->left = n->right = 0;
	n->v = v;
	return n;
}

void tree_insert(node **root, node *n)
{
	while (*root) root = ((*root)->v > n->v)
				? &(*root)->left
				: &(*root)->right;
	*root = n;
}

void tree_trav(int x)
{
	co_t *c = (co_t *) x;

	void trav(node *root) {
		if (!root) return;
		trav(root->left);
		co_yield(c, root);
		trav(root->right);
	}

	trav(c->in);
}

int tree_eq(node *t1, node *t2)
{
	co_t *c1 = co_new(tree_trav, t1);
	co_t *c2 = co_new(tree_trav, t2);

	node *p = 0, *q = 0;
	do {
		p = co_collect(c1);
		q = co_collect(c2);
	} while (p && q && (p->v == q->v));

	co_del(c1);
	co_del(c2);
	return !p && !q;
}

int main()
{
	int x[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1 };
	int y[] = { 2, 5, 7, 1, 9, 0, 6, 4, 8, 3, -1 };
	int z[] = { 0, 1, 2, 3, 4, 5, 6, 8, 9, -1 };

	node *t1 = 0, *t2 = 0, *t3 = 0;

	void mktree(int *buf, node **root) {
		int i;
		for (i = 0; buf[i] >= 0; i++)
			tree_insert(root, newnode(buf[i]));
	}

	mktree(x, &t1); 
	mktree(y, &t2); 
	mktree(z, &t3);

	printf("t1 == t2: %s\n", tree_eq(t1, t2) ? "yes" : "no");
	printf("t1 == t3: %s\n", tree_eq(t1, t3) ? "yes" : "no");

	return 0;
}





Java: import java.util.*;

class SameFringe
{
  public interface Node<T extends Comparable<? super T>>
  {
    Node<T> getLeft();
    Node<T> getRight();
    boolean isLeaf();
    T getData();
  }
  
  public static class SimpleNode<T extends Comparable<? super T>> implements Node<T>
  {
    private final T data;
    public SimpleNode<T> left;
    public SimpleNode<T> right;
    
    public SimpleNode(T data)
    {  this(data, null, null);  }
    
    public SimpleNode(T data, SimpleNode<T> left, SimpleNode<T> right)
    {
      this.data = data;
      this.left = left;
      this.right = right;
    }
    
    public Node<T> getLeft()
    {  return left;  }
    
    public Node<T> getRight()
    {  return right;  }
    
    public boolean isLeaf()
    {  return ((left == null) && (right == null));  }
    
    public T getData()
    {  return data;  }
    
    public SimpleNode<T> addToTree(T data)
    {
      int cmp = data.compareTo(this.data);
      if (cmp == 0)
        throw new IllegalArgumentException("Same data!");
      if (cmp < 0)
      {
        if (left == null)
          return (left = new SimpleNode<T>(data));
        return left.addToTree(data);
      }
      if (right == null)
        return (right = new SimpleNode<T>(data));
      return right.addToTree(data);
    }
  }
  
  public static <T extends Comparable<? super T>> boolean areLeavesSame(Node<T> node1, Node<T> node2)
  {
    Stack<Node<T>> stack1 = new Stack<Node<T>>();
    Stack<Node<T>> stack2 = new Stack<Node<T>>();
    stack1.push(node1);
    stack2.push(node2);
    
    while (((node1 = advanceToLeaf(stack1)) != null) & ((node2 = advanceToLeaf(stack2)) != null))
      if (!node1.getData().equals(node2.getData()))
        return false;
    
    return (node1 == null) && (node2 == null);
  }
  
  private static <T extends Comparable<? super T>> Node<T> advanceToLeaf(Stack<Node<T>> stack)
  {
    while (!stack.isEmpty())
    {
      Node<T> node = stack.pop();
      if (node.isLeaf())
        return node;
      Node<T> rightNode = node.getRight();
      if (rightNode != null)
        stack.push(rightNode);
      Node<T> leftNode = node.getLeft();
      if (leftNode != null)
        stack.push(leftNode);
    }
    return null;
  }
  
  public static void main(String[] args)
  {
    SimpleNode<Integer> headNode1 = new SimpleNode<Integer>(35, new SimpleNode<Integer>(25, new SimpleNode<Integer>(15, new SimpleNode<Integer>(10), new SimpleNode<Integer>(20)), new SimpleNode<Integer>(30)), new SimpleNode<Integer>(45, new SimpleNode<Integer>(40), new SimpleNode<Integer>(50)));
    SimpleNode<Integer> headNode2 = new SimpleNode<Integer>(24, new SimpleNode<Integer>(14, new SimpleNode<Integer>(10), new SimpleNode<Integer>(16, null, new SimpleNode<Integer>(20))), new SimpleNode<Integer>(34, new SimpleNode<Integer>(30), new SimpleNode<Integer>(42, new SimpleNode<Integer>(40), new SimpleNode<Integer>(56, new SimpleNode<Integer>(50), null))));
    SimpleNode<Integer> headNode3 = new SimpleNode<Integer>(24, new SimpleNode<Integer>(14, new SimpleNode<Integer>(10), new SimpleNode<Integer>(16, null, new SimpleNode<Integer>(20))), new SimpleNode<Integer>(34, new SimpleNode<Integer>(30), new SimpleNode<Integer>(42, new SimpleNode<Integer>(40), new SimpleNode<Integer>(50, null, new SimpleNode<Integer>(56)))));
    System.out.print("Leaves for set 1: ");
    simpleWalk(headNode1);
    System.out.println();
    System.out.print("Leaves for set 2: ");
    simpleWalk(headNode2);
    System.out.println();
    System.out.print("Leaves for set 3: ");
    simpleWalk(headNode3);
    System.out.println();
    System.out.println("areLeavesSame(1, 2)? " + areLeavesSame(headNode1, headNode2));
    System.out.println("areLeavesSame(2, 3)? " + areLeavesSame(headNode2, headNode3));
  }
  
  public static void simpleWalk(Node<Integer> node)
  {
    if (node.isLeaf())
      System.out.print(node.getData() + " ");
    else
    {
      Node<Integer> left = node.getLeft();
      if (left != null)
        simpleWalk(left);
      Node<Integer> right = node.getRight();
      if (right != null)
        simpleWalk(right);
    }
  }
}