160. Intersection of Two Linked Lists
Write a program to find the node at which the intersection of two singly linked lists begins.
For example, the following two linked lists:
A: a1 → a2
↘
c1 → c2 → c3
↗
B: b1 → b2 → b3
begin to intersect at node c1.
Notes:
- If the two linked lists have no intersection at all, return
null. - The linked lists must retain their original structure after the function returns.
- You may assume there are no cycles anywhere in the entire linked structure.
- Your code should preferably run in O(n) time and use only O(1) memory.
题意：
给定两个链表，求两个链表的交点（如果没有交点返回null）
思路：
对于两个相交的链表的来说，较长的链表 比 较短的链表 多出的部分（后对齐）肯定不是相交的部分，所以把 较长的链表的向后移动，直到长度相同，再重新遍历，相同即相遇。
public class Solution { public ListNode getIntersectionNode(ListNode headA, ListNode headB) { int lenA = length(headA), lenB = length(headB); // move headA and headB to the same start point while (lenA > lenB) { headA = headA.next; lenA--; } while (lenA < lenB) { headB = headB.next; lenB--; } // find the intersection until end while (headA != headB) { headA = headA.next; headB = headB.next; } return headA; } private int length(ListNode node) { int length = 0; while (node != null) { node = node.next; length++; } return length; } }
