题解 | #牛群的轴对称结构#

1.万能的队列

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return bool布尔型
     */
    bool check(pair<TreeNode*, TreeNode*> st){
        queue<pair<TreeNode*, TreeNode*> > q;
        q.push(st);
        while(!q.empty()){
            TreeNode* t1 = q.front().first;
            TreeNode* t2 = q.front().second;
            q.pop();
            if(!t1&&!t2) continue;
            if(!t1||!t2||(t1->val!=t2->val)) return false;
            q.push(make_pair(t1->left,t2->right));
            q.push(make_pair(t1->right,t2->left));
        }
        return true;
    }
    bool isSymmetric(TreeNode* root) {
        // write code here
        if(!root) return true;
        return check(make_pair(root,root));
    }
};