text: #include <stdlib.h>
  struct ListNode {
      int val;
      struct ListNode *next;
  };
  
  struct ListNode* swapnode(struct ListNode* head, int k)
  {
      struct ListNode* node[100000];
      int i = 0;
      for (;  head != NULL; head = head->next, i++)
          node[i] = head;
      int t = node[k-1]->val;
      node[k-1]->val = node[i-k]->val;
      node[i-k]->val = t;
      
      return node[0];
  }
  