【数据结构与算法】重建二叉树

只能根据前序中序或者中序后序重建二叉树，不可能根据前序和后序重建，因为需要中序去划分左右子树。

• 代码实现

/**
 * 源码名称：ConstructBT.java
 * 日期：2014-09-05
 * 程序功能：重建二叉树（前序中序）
 * 版权：[email protected]
 * 作者：A2BGeek
 */
public class ConstructBT {
	class Node<T> {
		T mValue;
		Node<T> mLeft;
		Node<T> mRight;

		public Node(T value, Node<T> left, Node<T> right) {
			mValue = value;
			mLeft = left;
			mRight = right;
		}
	}

	public Node<Character> buildBT(String pre, String mid) {
		Node<Character> root = null;
		String lpre, rpre, lmid, rmid;
		int pos = 0;
		if (pre.length() == 0 || mid.length() == 0) {
			return null;
		} else {
			root = new Node<Character>(pre.charAt(0), null, null);
			while (mid.charAt(pos) != root.mValue) {
				pos++;
			}
			// recursive left
			lpre = pre.substring(1, pos + 1);
			lmid = mid.substring(0, pos);
			root.mLeft = buildBT(lpre, lmid);
			// recursive right
			rpre = pre.substring(pos + 1, pre.length());
			rmid = mid.substring(pos + 1, mid.length());
			root.mRight = buildBT(rpre, rmid);
		}
		return root;
	}

	public void postIterate(Node<Character> root) {
		if (root == null) {
			return;
		} else {
			postIterate(root.mLeft);
			postIterate(root.mRight);
			System.out.print(root.mValue + " ");
		}
	}

	public static void main(String[] args) {
		ConstructBT bt = new ConstructBT();
		Node<Character> root = bt.buildBT("12473568", "47215386");
		bt.postIterate(root);
	}
}