Same Tree 判断俩树是不是一样

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.csdn.net/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;   
        }   
    }