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kartikkukreja/cycle-in-linked-list-hashset.cpp

Last active October 17, 2016 02:11
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Detecting a cycle in a linked list with a hashset
Raw
cycle-in-linked-list-hashset.cpp
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
ListNode* detectCycle(ListNode* A) {
unordered_set<ListNode*> seen;
for (ListNode* i = A; i != NULL; i = i->next) {
if (seen.find(i) != seen.end())
return i;
seen.insert(i);
}
return NULL;
}
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