1
var swapNodes = function (head, k) {
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  let A = head,
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    B = head,
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    K,
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    temp;
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  for (let i = 1; i < k; i++) A = A.next;
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  (K = A), (A = A.next);
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  while (A) (A = A.next), (B = B.next);
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  (temp = K.val), (K.val = B.val), (B.val = temp);
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  return head;
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};