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MergedLists.cpp
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MergedLists.cpp
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class MergedLists {
public:
bool check_lists_join(ListNode* a, ListNode* b) {
if (!a && !b) {
return true;
} else if (!a || !b) {
return false;
}
ListNode* a_tail = get_tail(a);
ListNode* b_tail = get_tail(b);
if (!a_tail->next && !b_tail->next) {
// neither list have cycle
return a_tail == b_tail;
} else if (a_tail->next && b_tail->next) {
// both lists have cycle
return is_same_cycle(a_tail, b_tail);
} else {
// one has cycle the other does not
return false;
}
}
private:
// if no cycle return tail, else return some node in the cycle
ListNode* get_tail(ListNode* head) {
ListNode *slow = head, *fast = head;
while (fast->next && fast->next->next) {
slow = slow->next;
fast = fast->next->next;
if (slow == fast) {
return slow;
}
}
return fast->next ? fast->next : fast;
}
bool is_same_cycle(ListNode* a, ListNode* b) {
ListNode* cur = a->next;
while (cur != a) {
if (cur == b) {
return true;
}
cur = cur->next;
}
return false;
}
};