leetcode 相交链表

160. 相交链表

哈希表

func getIntersectionNode(headA, headB *ListNode) *ListNode {
    hmap := make(map[*ListNode]struct{})
    for headA != nil {
        hmap[headA] = struct{}{}
        headA = headA.Next
    }
    for headB != nil {
        if _,ok := hmap[headB]; ok {
            return headB
        }
        headB = headB.Next
    }
    return nil
}

双指针，实现空间复杂度O(1)

func getIntersectionNode(headA, headB *ListNode) *ListNode {
    if headA == nil || headB == nil {
        return nil
    }
    pa, pb := headA, headB
    for pa != pb {
        if pa == nil {
            pa = headB
        } else {
            pa = pa.Next
        }
        if pb == nil {
            pb = headA
        } else {
            pb = pb.Next
        }
    }
    return pa
}