160.Intersection of Two Linked Lists

 

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def getIntersectionNode(self, headA: ListNode, headB: ListNode) -> ListNode:
        lenA, lenB = 0, 0
        pA, pB = headA, headB
        while pA:
            lenA += 1
            pA = pA.next
        while pB:
            lenB += 1
            pB = pB.next
        if lenA > lenB:
            for _ in range(lenA - lenB):
                headA = headA.next
        else:
            for _ in range(lenB - lenA):
                headB = headB.next
        while headA:
            if headA == headB:
                return headA
            else:
                headA = headA.next
                headB = headB.next
        return None