作者：百变精装绣 | 来源：互联网 | 2023-10-09 22:26
本文由编程笔记#小编为大家整理，主要介绍了160.IntersectionofTwoLinkedLists-Easy相关的知识，希望对你有一定的参考价值。Writ
本文由编程笔记#小编为大家整理，主要介绍了160. Intersection of Two Linked Lists - Easy相关的知识，希望对你有一定的参考价值。
Write a program to find the node at which the intersection of two singly linked lists begins.
For example, the following two linked lists:
begin to intersect at node c1.
Example 1:
Input: intersectVal = 8, listA = [4,1,8,4,5], listB = [5,0,1,8,4,5], skipA = 2, skipB = 3
Output: Reference of the node with value = 8
Input Explanation: The intersected node‘s value is 8 (note that this must not be 0 if the two lists intersect). From the head of A, it reads as [4,1,8,4,5]. From the head of B, it reads as [5,0,1,8,4,5]. There are 2 nodes before the intersected node in A; There are 3 nodes before the intersected node in B.
Example 2:
Input: intersectVal = 2, listA = [0,9,1,2,4], listB = [3,2,4], skipA = 3, skipB = 1
Output: Reference of the node with value = 2
Input Explanation: The intersected node‘s value is 2 (note that this must not be 0 if the two lists intersect). From the head of A, it reads as [0,9,1,2,4]. From the head of B, it reads as [3,2,4]. There are 3 nodes before the intersected node in A; There are 1 node before the intersected node in B.
Example 3:
Input: intersectVal = 0, listA = [2,6,4], listB = [1,5], skipA = 3, skipB = 2
Output: null
Input Explanation: From the head of A, it reads as [2,6,4]. From the head of B, it reads as [1,5]. Since the two lists do not intersect, intersectVal must be 0, while skipA and skipB can be arbitrary values.
Explanation: The two lists do not intersect, so return null.
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.
two pointers
p1 p2分别从A B head开始，当p1走完A，redirect to head of B，当p2走完B, redirect to head of A，如果它们有intersection，就会相遇
如果有intersection，两个list的最后节点是相同的，比较最后两个节点，如果不同，说明没有intersection，返回null
time: O(m + n), space: O(1)
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
if(headA == null || headB == null) {
return null;
}
ListNode p1 = headA, p2 = headB;
while(p1 != p2) {
p1 = (p1 == null) ? headB : p1.next;
p2 = (p2 == null) ? headA : p2.next;
}
return p1;
}
}
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