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Intersection of Two Linked Lists

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Description

https://leetcode.com/problems/intersection-of-two-linked-lists/description/

Solution

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/**
 * 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 == NULL || headB == NULL) return NULL;
        int lengthA = 0;
        int lengthB = 0;
        ListNode* traverseA = headA;
        ListNode* traverseB = headB;
        while(traverseA != NULL) {
            traverseA = traverseA->next;
            lengthA += 1;
        }
        while(traverseB != NULL) {
            traverseB = traverseB->next;
            lengthB += 1;
        }
        if (lengthA > lengthB) {
            int gap = lengthA - lengthB;
            while(gap > 0) {
                headA = headA->next;
                gap -= 1;
            }
        }else {
            int gap = lengthB - lengthA;
            while(gap > 0) {
                headB = headB->next;
                gap -= 1;
            }
        }
        while(headA != NULL && headB != NULL && headA != headB) {
            headA = headA->next;
            headB = headB->next;
        }
        return headA;
    }
};