-
Notifications
You must be signed in to change notification settings - Fork 3
/
156.cpp
57 lines (54 loc) · 1.75 KB
/
156.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
/**
* 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* upsideDownBinaryTree(TreeNode* root) {
if (!root) return root;
vector<vector<TreeNode*>> bfsResults;
queue<TreeNode*> q;
q.push(root);
int level = 0;
while (!q.empty()) {
int size = q.size();
for (int i = 0; i < size; ++i) {
TreeNode* node = q.front();
q.pop();
if (bfsResults.size() == level) bfsResults.push_back({node});
else bfsResults[level].push_back(node);
if (node->left) q.push(node->left);
if (node->right) q.push(node->right);
}
level++;
}
level--;
TreeNode* newRoot = bfsResults[level][0];
TreeNode* current = newRoot;
while (level >= 0) {
TreeNode* currentLevel = current;
int n = bfsResults[level].size();
for (int i = 1; i < n; ++i) {
currentLevel->left = bfsResults[level][i];
currentLevel = currentLevel->left;
}
currentLevel->left = nullptr;
if (level - 1 >= 0) {
current->right = bfsResults[level - 1][0];
current = current->right;
}
else {
current->right = nullptr;
}
level--;
}
return newRoot;
}
};