[LeetCode] Invert Binary Tree - 二叉树翻转系列问题

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
 //思路：二叉树递归 左右结点交换 在递归翻转左右子树
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        TreeNode *left, *right;
        if(root==NULL)
            return root;
        left = root->left;
        right = root->right;
        root->left = invertTree(right);
        root->right = invertTree(left);
        return root;
    }
};

//第二种方法 通过队列层次遍历队列实现
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        queue<TreeNode*> q;
        if(root==NULL)
            return root;
        q.push(root);
        int size=q.size();
        while(size>0)
        {
            TreeNode *p=q.front();
            q.pop();
            //交换左右结点
            TreeNode *LNode=p->left;
            TreeNode *RNode=p->right;
            p->left=RNode;
            p->right=LNode;
            //进入队列
            if(p->left) {
                q.push(p->left);
            }
            if(p->right) {
                q.push(p->right);
            }
            size=q.size();
        }
        return root;
    }
};