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117.cpp
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117.cpp
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/*
// Definition for a Node.
class Node {
public:
int val;
Node* left;
Node* right;
Node* next;
Node() : val(0), left(NULL), right(NULL), next(NULL) {}
Node(int _val) : val(_val), left(NULL), right(NULL), next(NULL) {}
Node(int _val, Node* _left, Node* _right, Node* _next)
: val(_val), left(_left), right(_right), next(_next) {}
};
*/
class Solution {
public:
Node* connect(Node* root) {
Node* dummy = new Node(-1); // linked list for next level
Node* head = root;
Node* curr = dummy;
while (root) {
if (root->left) {
curr->next = root->left;
curr = curr->next;
}
if (root->right) {
curr->next = root->right;
curr = curr->next;
}
root = root->next;
// go to next level
if (!root) {
curr = dummy;
root = dummy->next;
dummy->next = nullptr;
}
}
return head;
}
};