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Leetcode-Intersection of Two Linked Lists

2024-08-05 02:42:03   212人阅读

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.

Solution:

 1 /** 2  * Definition for singly-linked list. 3  * public class ListNode { 4  *     int val; 5  *     ListNode next; 6  *     ListNode(int x) { 7  *         val = x; 8  *         next = null; 9  *     }10  * }11  */12 public class Solution {13     public ListNode getIntersectionNode(ListNode headA, ListNode headB) {14         if (headA==null || headB==null) return null;15 16         ListNode s1 = headA;17         ListNode s2 = headB;18         int len1 = 1;19         while (s1.next!=null){20             len1++;21             s1 = s1.next;22         }23         int len2 = 1;24         while (s2.next!=null){25             len2++;26             s2=s2.next;27         }28         s1 = headA;29         s2 = headB;30         if (len1>len2){31             while (len1>len2){32                 s1 = s1.next;33                 len1--;34             }35         } else if (len1<len2){36             while (len1<len2){37                 s2 = s2.next;38                 len2--;39             }40         }41 42         while (s1!=null && s2!=null){43             if (s1==s2)44                 return s1;45             s1 = s1.next;46             s2 = s2.next;47         }48 49         return null;50     }51 }

 

Leetcode-Intersection of Two Linked Lists


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