二叉树的镜像

1.递归法

void Mirror(TreeNode *pRoot) {
        if(!pRoot || (pRoot->left == nullptr && pRoot->right == nullptr))return;//或者只是if(!pRoot)
        TreeNode* temp = pRoot->left;
        pRoot->left = pRoot->right;
        pRoot->right = temp;
        if(pRoot->left)Mirror(pRoot->left);
        if(pRoot->right)Mirror(pRoot->right);
    }

2.非递归

void Mirror(TreeNode *pRoot) {
        if(!pRoot)return;
        queue<TreeNode*> q;
        q.push(pRoot);
        TreeNode *tr, *temp;
        while(!q.empty()){
            tr = q.front();
            if(tr->left || tr->right){
                temp = tr->left;
                tr->left = tr->right;
                tr->right = temp;
                if(tr->left)q.push(tr->left);
                if(tr->right)q.push(tr->right);
            }
            q.pop();
        }
    }