21树的子结构--剑指offer，java版

21树的子结构–剑指offer，java版

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

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

}

}
*/
public class Solution {
//第一步判断：A某一节点的值和B头节点相同
public boolean HasSubtree(TreeNode root1,TreeNode root2) {
boolean result = false;
if(root1 != null && root2 != null){
if(root1.val == root2.val)
result = DoesSubtree(root1,root2);
if(!result)
result = HasSubtree(root1.left,root2);
if(!result)
result = HasSubtree(root1.right,root2);
}
return result;
}
//再递归的判断左右节点的值是否相同
public boolean DoesSubtree(TreeNode node1,TreeNode node2){
if(node2 == null) return true;
if(node1 == null) return false;
if(node1.val != node2.val) return false;
return DoesSubtree(node1.left,node2.left) &&
DoesSubtree(node1.right,node2.right);
}
}