LeetCode226.翻转二叉树

题目

分析

翻转每个节点左右子树即可。

代码

前序遍历，递归法

class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if(root == NULL) return root;
        TreeNode* node = root->left;
        root->left = root->right; root->right = node;
        invertTree(root->left);
        invertTree(root->right);
        return root;
    }
};

 前序遍历，迭代法

class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if(root== NULL) return root;
        stack<TreeNode*>s;
        s.push(root);
        while(!s.empty()){
            auto t = s.top();
            s.pop();
            swap(t->left,t->right);
            if(t->right!=NULL) s.push(t->right);
            if(t->left!=NULL) s.push(t->left);
        }
        return root;
    }
};