Lintcode470-Tweaked Identical Binary Tree-Easy

470. Tweaked Identical Binary Tree

Check two given binary trees are identical or not. Assuming any number of tweaksare allowed. A tweak is defined as a swap of the children of one node in the tree.

Example

Example 1:

Input:{1,2,3,4},{1,3,2,#,#,#,4}
Output:true
Explanation:
        1             1
       /            / 
      2   3   and   3   2
     /                   
    4                     4

are identical.

Example 2:

Input:{1,2,3,4},{1,3,2,4} 
Output:false
Explanation:

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

are not identical.

Challenge

O(n) time

Notice

There is no two nodes with the same value in the tree.

思路：

tweaked identical tree 有两种情况，一种是b树是a树的tweak树（每个对应结点都交换），二是b树和a树完全相同。这两种情况为true。

思路和Lintcode469 Same tree相似，只是多一种组合。

代码：

/**
 * 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: the root of binary tree a.
     * @param b: the root of binary tree b.
     * @return: true if they are tweaked identical, or false.
     */
    public boolean isTweakedIdentical(TreeNode a, TreeNode b) {
        if (a == null && b == null) {
            return true;
        }
        else if (a != null && b != null) {
            return (a.val == b.val && isTweakedIdentical(a.left, b.left) 
                    && isTweakedIdentical(a.right, b.right))
                    ||(a.val == b.val && isTweakedIdentical(a.left, b.right) 
                    && isTweakedIdentical(a.right, b.left));
        }
        else {
            return false;
        }
    }
}