Intersection of Two Linked Lists — C++

// Time:  O(m + n)
// Space: O(1)

/**
 * 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) {
        ListNode *curA = headA, *curB = headB;
        while (curA != curB) {
            curA = curA ? curA->next : headB;
            curB = curB ? curB->next : headA;
        }
        return curA;
    }
};