算法-树

private static void createBinaryTree(TreeNode head ,int value) {
		if(head==null)
			return;
		TreeNode currentNode = head;
		while(true){
			if(value < currentNode.value){
				if(currentNode.left == null){
					currentNode.left = new TreeNode(value);
					return;
				}else
					currentNode = currentNode.left;
			}else{
				if(currentNode.right == null){
					currentNode.right = new TreeNode(value);
					return;
				}else
					currentNode = currentNode.right;
			}
		}
	}

private static String sequenceTree(TreeNode<Integer> head) {
	if(head==null)
		return "#!";
	String res = String.valueOf(head.item)+"!";
	res += sequenceTree(head.left);
	res += sequenceTree(head.right);
	return res;
}
// 使用前序遍历来反序列化
//  seq="10!3!2!#!#!4!#!7!5!#!#!9!8!#!#!#!11!#!12!#!20!#!23!#!#!"
private static TreeNode<Integer> reconByString(String seq) {
	String[] value = seq.split("!");
	Queue<String> queue = new LinkedList<String>();
	for(int i=0;i!=value.length;i++)
		queue.offer(value[i]);
	return reconPreOrder(queue);
}
private static TreeNode<Integer> reconPreOrder(Queue<String> queue) {
	String value =queue.poll();
	if(value.equals("#"))
		return null;
	TreeNode head = new TreeNode(Integer.valueOf(value));
	head.left = reconPreOrder(queue);
	head.right = reconPreOrder(queue);
	return head;
}
// 使用层次遍历来反序列化
private static String sequenceTreeByLevel(TreeNode head){
	if(head==null)
		return "#!";
	String res = head.value+"!";
	Queue<Node> queue = new LinkedList<Node>();
	queue.offer(head);
	while(!queue.isEmpty()){
		head = queue.poll();
		if(head.left!=null){
			res+=head.left.value+"!";
			queue.offer(head.left);
		}else{
			res+="#!";
		}
		if(head.right!=null){
			res+=head.right.value+"!";
			queue.offer(head.right);
		}else{
			res+="#!";
		}
	}
	return res;
}