Singly linked list inversion, without creating new nodes, only by recombining existing nodes_Complete singly linked list inversion without additional arrays or nodes_Whirlwind Charge Tornado_’s blog

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Algorithm idea:
To reverse the singly linked list, you should first think of using the head interpolation method, but it is required not to create a new node, you can use the elements in L as the insertion object, and set L->next to empty. Then the elements are inserted into L one by one using the head interpolation method.

void reverse(LNode* L) {
     
 LNode* p = L->next;
 LNode* q;
 L->next = NULL;
 while (p) {
     
 q = p->next;//q is used to record the successor node of p
 p->next = L->next;//The node pointed to by p is inserted into a new linked list
 L->next = p;
 p = q;
 }
 }