【LeetCode】Identical Binary Tree等价二叉树 - Easy+

等价二叉树 

1             1
/ \           / \
2   2   and   2   2
/             /
4             4

1             1
/ \           / \
2   3   and   2   3
/               \
4                 4

/**
* Definition of TreeNode:
* public class TreeNode {
*     public int val;
*     public TreeNode left, right;
*     public TreeNode(int val) {
*         this.val = val;
*         this.left = this.right = null;
*     }
* }
*/
public class Solution {
/**
* @param a, b, the root of binary trees.
* @return true if they are identical, or false.
*/
public boolean isIdentical(TreeNode a, TreeNode b) {
if(a == null && b == null){
return true;
}
if(a == null && b != null|| a != null & b == null){
return false;
}
return a.val == b.val && isIdentical(a.left,b.left)
&& isIdentical(a.right,b.right);
//等价条件：判断两棵Tree是否同构，同构的定义是可以通过交换左右子树使得他们相同
}
}