Leetcode:intersection of Linked Lists

Intersection of Linked Lists

Total Accepted: 74850 Total Submissions: 246823 Difficulty: Easy

Write a program to find the node at which the intersection of the singly linked lists begins.

For example, the following, linked lists:

A:          a1→a2                                        c1→c2→c3                               B:     b1→b2→b3

Begin to intersect at node C1.

Notes:

• If The linked lists has no intersection at all, return null .
• The linked lists must retain their original structure after the function returns.
• You may assume there is no cycles anywhere in the entire linked structure.
• Your code should preferably run in O (n) time and use only O (1) memory.

Credits:
Special thanks to @stellari for adding this problem and creating all test cases.

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C + + code:

/** * Definition for singly-linked list. * struct ListNode {* int val; * ListNode *next; * ListNode (int x): Val (x), Next (NULL) {} *};  */class Solution {Public:listnode *getintersectionnode (ListNode *heada, ListNode *headb) {if (!headA | |!headB)        return NULL;        int cnta=0,cntb=0;        ListNode *pa=heada, *pb=headb;            while (PA) {pa=pa->next;        cnta++;            } while (Pb) {pb=pb->next;        cntb++;        } pa=heada,pb=headb;            while (Cntb < CntA) {pa=pa->next;        cnta--;            } while (CntA < CNTB) {pb=pb->next;        cntb--;            } while (PA && pb) {if (PA = = pb) break;                else{pa=pa->next;            pb=pb->next;    }} return PA; }};

Leetcode:intersection of Linked Lists