BFS()方法进行题解。

C++ 代码

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int f,len;
    bool isSymmetric(TreeNode* root) {
        if(!root) return true;
        return bfs(root);
    }
    bool bfs(TreeNode* root)
    {
        queue<TreeNode*> q;
        q.push(root);

        while(q.size())
        {
            len=q.size();
            if(f==1)
            {
                if(len%2) return false;
            }
            int v[len*2]={0};
            for(int i=0;i<len;i++)
            {
                auto t = q.front();
                q.pop();
                if(t->left)
                {
                    q.push(t->left);
                    v[i*2]=t->left->val;
                }
                if(t->right)
                {
                    q.push(t->right);
                    v[i*2+1]=t->right->val;
                }
            }
            for(int i=0;i<len*2;i++)
            {
                if(v[i]!=v[2*len-1-i]) return false;
            }
            f=1;
        }
        return true;
    }
};