LeetCode(100)-Same Tree

版权声明：XiangYida https://blog.csdn.net/qq_36781505/article/details/83854553

100. Same Tree

Given two binary trees, write a function to check if they are the same or not.
Two binary trees are considered the same if they are structurally identical and the nodes have the same value.
Example 1:
Input: 1 1
/ \ /
2 3 2 3
[1,2,3], [1,2,3]
Output: true
Example 2:
Input: 1 1
/
2 2
[1,2], [1,null,2]
Output: false
Example 3:
Input: 1 1
/ \ /
2 1 1 2
[1,2,1], [1,1,2]
Output: false

这个题的意思就是给两个二叉树，然后判断两个二叉树是否相同
原本采用的递归方法中序遍历，然后在比较，但是最后一个用例老是通过不了，先占时把代码放上，以后再研究下

public boolean isSameTree(TreeNode p, TreeNode q) {
        if(p==null&&q==null)return  true;
        if(q==null&&p!=null||q!=null&&p==null)return  false;
        List<Integer> list1=new LinkedList<>();
        List<Integer> list2=new LinkedList<>();
        helper(p,list1);
        helper(q,list2);
        if (list1.equals(list2))return true;
        return false;
    }

    public void helper(TreeNode treeNode, List<Integer>list){
        list.add(treeNode.val);
        if(treeNode.left!=null){
            treeNode=treeNode.left;
            helper(treeNode,list);
        }else list.add(0);
        if(treeNode.right!=null){
            treeNode=treeNode.right;
            helper(treeNode,list);
        }list.add(0);
    }

后来看大神的代码，果然很nice

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