根据前序遍历和中序遍历重建二叉树的Java实现

package cn.feng;
class Node {
	Node left = null;
	Node right = null;
	char value;
}
public class BinaryTreeBuilder {
	/**
	 * 根据前序遍历和中序遍历重建二叉树子树
	 * @param preOrder 前序遍历数组
	 * @param start 子树起始位置
	 * @param inOrder 中序遍历数组
	 * @param end 中序遍历结束位置
	 * @param length 子树节点树
	 * @return 子树的根节点
	 */
	public static Node buildTree(char[] preOrder, int start,
			char[] inOrder, int end, int length) {
		//参数验证
		if (preOrder == null || preOrder.length == 0 || inOrder == null
				|| inOrder.length == 0 || length <= 0) {
			return null;
		}
		
		//建立子树根节点
		char value = preOrder[start];
		Node root = new Node();
		root.value = value;
		
		//递归终止条件：子树只有一个节点
		if (length == 1)
			return root;
		
		//分拆子树的左子树和右子树
		int i = 0;
		while (i < length) {
			if (value == inOrder[end - i]) {
				break;
			}
			i++;
		}
		
		//建立子树的左子树
		root.left = buildTree(preOrder, start + 1, inOrder, end - i - 1, length - 1 - i);
		//建立子树的右子树
		root.right = buildTree(preOrder, start + length - i, inOrder, end, i );
		
		return root;
	}
	public static void main(String[] args) {
		char[] preOrder = new char[] {'a', 'b', 'd', 'c', 'e', 'f'};
		char[] inOrder = new char[] {'d', 'b', 'a', 'e', 'c', 'f'};
		Node root = buildTree(preOrder, 0, inOrder, inOrder.length - 1, inOrder.length);
	}
}