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, returnnull.
• 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 shocould preferably run in O (n) time and use only O (1) memory.

1/** 2 * definition for singly-linked list. 3 * struct listnode {4 * int val; 5 * listnode * Next; 6 * listnode (int x): Val (x), next (null) {} 7 *}; 8 */
// The difference between a long-chain table and a short linked list before the intersection is the difference between the total length of the two linked lists.
9 class solution {10 public: 11 listnode * getintersectionnode (listnode * heada, listnode * headb) {12 if (heada = nullptr | headb = nullptr) return nullptr; 13 else {14 int Lena = 0; int lenb = 0; 15 auto * ptr1 = heada; 16 auto * ptr2 = headb; 17 while (ptr1) {18 ++ Lena; ptr1 = ptr1-> next; 19} 20 while (ptr2) {21 + + lenb; ptr2 = ptr2-> next; 22} 23 int diff = (Lena> lenb )? Lena-lenb: lenb-Lena; 24 ptr1 = heada; ptr2 = headb; 25 if (Lena> lenb) {26 while (diff --) {27 ptr1 = ptr1-> next; 28} 29} else if (lenb> Lena) {30 While (diff --) {31 ptr2 = ptr2-> next; 32} 33} 34 while (ptr1! = Ptr2) {35 ptr1 = ptr1-> next; ptr2 = ptr2-> next; 36} 37 return ptr1; 38} 39} 40 };

 

160. intersection of two linked lists