Mind palace

some thoughts

0%

226. Invert Binary Tree

Posted on In Disqus:
Symbols count in article: 1.2k Reading time ≈ 1 mins. 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if (!root) return root;
        auto t = root->left;
        root->left = invertTree(root->right);
        root->right = invertTree(t);
        return root;
    }
};
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if (!root) return root;
        auto l = invertTree(root->left);
        auto r = invertTree(root->right);
        root->left = r;
        root->right = l;
        return root;
    }
};
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* & invertTree(TreeNode* &root) { // 必须返回ref，否则不能swap
        if (!root) return root;
        swap(invertTree(root->left), invertTree(root->right));
        return root;
    }
};