代码
/*
// 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) {
if (!root) return root;
auto ans = root;
while (root->left) {
for (auto p = root; p; p = p->next) {
p->left->next = p->right;
if (p->next) p->right->next = p->next->left;
}
root = root->left;
}
return ans;
}
};