当前位置 博文首页 > Aaron_Yang:LeetCode226:翻转二叉树(递归法+迭代法)
翻转一棵二叉树。
我用的是前序遍历,所以先进行交换左右孩子结点,然后反转左子树,反转右子树。
/**
* 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:
TreeNode* invertTree(TreeNode* root) {
if(root ==nullptr) return root;
swap(root->left,root->right);
invertTree(root->left);
invertTree(root->right);
return root;
}
};
用栈实现二叉树的深度优先遍历,稍微改一点点就可以。
/**
* 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:
TreeNode* invertTree(TreeNode* root) {
if(root==nullptr) return root;
stack<TreeNode*>st;
st.push(root);
while(!st.empty())
{
TreeNode *node = st.top();
st.pop();
swap(node->left,node->right);
if(node->right) st.push(node->right);
if(node->left) st.push(node->left);
}
return root;
}
};
cs