160. Intersection of Two Linked Lists ¶

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

C++JavaPythonJavaScript

class Solution {
 public:
  ListNode* getIntersectionNode(ListNode* headA, ListNode* headB) {
    ListNode* a = headA;
    ListNode* b = headB;

    while (a != b) {
      a = a == nullptr ? headB : a->next;
      b = b == nullptr ? headA : b->next;
    }

    return a;
  }
};

class Solution {
  public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
    ListNode a = headA;
    ListNode b = headB;

    while (a != b) {
      a = a == null ? headB : a.next;
      b = b == null ? headA : b.next;
    }

    return a;
  }
}

class Solution:
  def getIntersectionNode(
      self,
      headA: ListNode,
      headB: ListNode,
  ) -> ListNode | None:
    a = headA
    b = headB

    while a != b:
      a = a.next if a else headB
      b = b.next if b else headA

    return a

var getIntersectionNode = function(headA, headB) {
  let a = headA, b = headB;
  while (a !== b) {
    a = a ? a.next : headB;
    b = b ? b.next : headA;
  }
  return a;
};