forked from cmhungsteve/LeetCode
-
Notifications
You must be signed in to change notification settings - Fork 0
/
invert-binary-tree.cpp
77 lines (73 loc) · 1.84 KB
/
invert-binary-tree.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
// Time: O(n)
// Space: O(h)
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
// Time: O(n)
// Space: O(w), w is the max number of nodes of the levels.
// BFS solution.
class Solution {
public:
TreeNode* invertTree(TreeNode* root) {
if (root != nullptr) {
queue<TreeNode*> nodes;
nodes.emplace(root);
while (!nodes.empty()) {
auto node = nodes.front();
nodes.pop();
swap(node->left, node->right);
if (node->left != nullptr) {
nodes.emplace(node->left);
}
if (node->right != nullptr) {
nodes.emplace(node->right);
}
}
}
return root;
}
};
// Time: O(n)
// Space: O(h)
// Stack solution.
class Solution2 {
public:
TreeNode* invertTree(TreeNode* root) {
if (root != nullptr) {
stack<TreeNode*> nodes;
nodes.emplace(root);
while (!nodes.empty()) {
auto node = nodes.top();
nodes.pop();
swap(node->left, node->right);
if (node->left != nullptr) {
nodes.emplace(node->left);
}
if (node->right != nullptr) {
nodes.emplace(node->right);
}
}
}
return root;
}
};
// Time: O(n)
// Space: O(h)
// DFS, Recursive solution.
class Solution3 {
public:
TreeNode* invertTree(TreeNode* root) {
if (root != nullptr) {
swap(root->left, root->right);
invertTree(root->left);
invertTree(root->right);
}
return root;
}
};