剑指offer编程题（JAVA实现)——第17题：树的子结构

github	https://github.com/JasonZhangCauc/JZOffer

/**
 * 
 * 剑指offer编程题（JAVA实现)——树的子结构
 * 
 * 题目描述
 * 输入两棵二叉树A，B，判断B是不是A的子结构。（ps：我们约定空树不是任意一个树的子结构）
 *
 */
public class Test17 {

	public boolean HasSubtree(TreeNode root1, TreeNode root2) {
		if (root1 == null || root2 == null) {
			return false;
		}
		boolean flag = false;
		if (root1.val == root2.val) {
			flag = isSubTree(root1, root2);
			if (flag) {
				return true;
			} else {
				return HasSubtree(root1.left, root2) || HasSubtree(root1.right, root2);
			}
		}
		return flag;
	}

	private boolean isSubTree(TreeNode root1, TreeNode root2) {
		if (root2 == null) {
			return true;
		}
		if (root1 == null && root2 != null) {
			return false;
		}
		if (root1.val == root2.val) {
			return isSubTree(root1.left, root2.left) && isSubTree(root1.right, root2.right);
		} else {
			return false;
		}

	}


	public class TreeNode {
		int val = 0;
		TreeNode left = null;
		TreeNode right = null;

		public TreeNode(int val) {
			this.val = val;

		}
	}
}