代码解决

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool isSameTree(TreeNode* p, TreeNode* q) 
    {
        if (p == nullptr && q == nullptr) {
            return true;
        } else if (p == nullptr || q == nullptr) {
            return false;
        }
        queue<TreeNode*> que1;
        if(p!=nullptr) que1.push(p);
        queue<TreeNode*> que2;
        if(q!=nullptr) que2.push(q);
        while(!que1.empty()&&!que2.empty())
        {
            auto node1=que1.front();
            que1.pop();
            auto node2=que2.front();
            que2.pop();
            if(node1->val!=node2->val)
            {
                return false;
            }
            auto left1=node1->left,right1=node1->right,left2=node2->left,right2=node2->right;
            if ((left1 == nullptr) ^ (left2 == nullptr)) 
            {
                return false;
            }
            if ((right1 == nullptr) ^ (right2 == nullptr)) 
            {
                return false;
            }
            if (left1 != nullptr) {
                que1.push(left1);
            }
            if (right1 != nullptr) {
                que1.push(right1);
            }
            if (left2 != nullptr) {
                que2.push(left2);
            }
            if (right2 != nullptr) {
                que2.push(right2);
            }
        }
        return que1.empty()&&que2.empty();
    }
};

代码解决2 

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr, right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool isSameTree(TreeNode* p, TreeNode* q) 
    {
        // 如果两个节点都为空，则它们相同
        if(p==nullptr&&q==nullptr)
        {
            return true;
        }
        // 如果只有一个节点为空，则它们不同
        else if(p==nullptr||q==nullptr)
        {
            return false;
        }
        // 如果两个节点的值不同，则它们不同
        else if(p->val!=q->val)
        {
            return false;
        }
        // 递归地比较左子树和右子树
        else
        {
            return isSameTree(p->left,q->left)&&isSameTree(p->right,q->right);
        }
    }
};