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swapping-nodes-in-a-linked-list.dart (941B)

      1 //Swap two nodes in a linked list without swapping the values.
      2 //Basically place the kth element in the length - kth spot
      3 //and vice versa not just swap the stored values.
      4 //I did this using an array list where I swapped the nodes
      5 //and then went through the list setting the next node to be
      6 //n + 1. This was the easiest solution I could think of.
      7 //The time complexity of this is O(n) where n is the lenght of the
      8 //list.
      9 //Time: 465ms Beats: 50%
     10 //Memory: 212.2MB Beats: 25%
     11 class Solution {
     12   ListNode? swapNodes(ListNode? head, int k) {
     13     ListNode? itr = head;
     14     List<ListNode?> vals = [];
     15     while(itr != null){
     16       vals.add(itr);
     17       itr = itr.next;
     18     }
     19     
     20     ListNode? temp = vals[k - 1];
     21     vals[k - 1] = vals[vals.length - k];
     22     vals[vals.length - k] = temp;
     23     for(int i = 0 ; i < vals.length - 1 ; ++i){
     24       vals[i]?.next = vals[i + 1];
     25     }
     26     vals[vals.length - 1]?.next = null;
     27     return vals[0];
     28   }
     29 }