Partition List | Problems

Given a linked list and a value x, partition it so all nodes < x come before nodes >= x.

Example: head = [1,4,3,2,5,2], x = 3 → [1,2,2,4,3,5]

Sample Input

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Sample Output

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Constraints

0 to 200 nodes
-100 <= Node.val <= 100
-200 <= x <= 200

Topics

Linked List

Two Lists

function partition(head, x) {
  const before = {next:null}, after = {next:null};
  let b = before, a = after;
  while (head) {
    if (head.val < x) { b.next = head; b = b.next; }
    else { a.next = head; a = a.next; }
    head = head.next;
  }
  a.next = null; b.next = after.next;
  return before.next;
}

Time: O(n) | Space: O(1)

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