Same Tree 判断俩树是不是一样-优快云博客

本文提供两种方法来检查两棵二叉树是否等价，即它们是否在结构上完全相同且节点值相等。一种是递归方法，另一种是非递归的迭代方法。递归方法直观地比较两个树的节点，而迭代方法使用队列来逐层遍历并比较两棵树。

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Given two binary trees, write a function to check if they are equal or not.

Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

/**

* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/

下边的这个是递归

出处：http://www.bubuko.com/infodetail-954959.html

public class Solution {
    public boolean isSameTree(TreeNode p, TreeNode q) {
         if(p==null&&q==null) return true;
       if(p==null||q==null) return false;
       if(p.val!=q.val) return false;
       return isSameTree(p.left, q.left)&&isSameTree(p.right, q.right);
    }

}

下边的这个是迭代

出处：http://blog.youkuaiyun.com/xudli/article/details/8557010

  public class Solution {
        public boolean isSameTree(TreeNode p, TreeNode q) {
            Queue<TreeNode> q1 = new LinkedList<TreeNode>();
            Queue<TreeNode> q2 = new LinkedList<TreeNode>();

            q1.offer(p);
            q2.offer(q);

            while( !q1.isEmpty() && !q2.isEmpty() ) {
                TreeNode x = q1.poll();
                TreeNode y = q2.poll();

                if(x==null) {
                    if( y!=null) return false;
                    else continue;
                }

                if(y==null || x.val!=y.val) return false;

                q1.offer( x.left);
                q1.offer( x.right);
                q2.offer(y.left);
                q2.offer(y.right);
            }

            return true;
        }
    }