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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, 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.
/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {private: int calcListLength(ListNode *head) { int len = 0; while (head) { len++; head = head->next; } return len; }public: ListNode *getIntersectionNode(ListNode* headA, ListNode* headB) { int lenA = calcListLength(headA); int lenB = calcListLength(headB); if (lenA < lenB) { swap(headA, headB); swap(lenA,lenB); } ListNode* pA = headA; ListNode* pB = headB; int n = lenA - lenB; while (n--) { pA = pA->next; } while (lenB--) { if (pA == pB) return pA; pA = pA->next; pB = pB->next; } return nullptr; }};
Intersection of Two Linked Lists
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