LeetCode – Intersection of Two Linked Lists (Java)
Problem
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.
Java Solution
First calculate the length of two lists and find the difference. Then start from the longer list at the diff offset, iterate though 2 lists and find the node.
/** * Definition for singlylinked 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) { int len1 = 0; int len2 = 0; ListNode p1=headA, p2=headB; if (p1 == null  p2 == null) return null; while(p1 != null){ len1++; p1 = p1.next; } while(p2 !=null){ len2++; p2 = p2.next; } int diff = 0; p1=headA; p2=headB; if(len1 > len2){ diff = len1len2; int i=0; while(i<diff){ p1 = p1.next; i++; } }else{ diff = len2len1; int i=0; while(i<diff){ p2 = p2.next; i++; } } while(p1 != null && p2 != null){ if(p1.val == p2.val){ return p1; } p1 = p1.next; p2 = p2.next; } return null; } } 
<pre><code> String foo = "bar"; </code></pre>

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