70 lines
1.3 KiB
C++
70 lines
1.3 KiB
C++
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#include <bits/stdc++.h>
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using namespace std;
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/* Link list node */
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struct Node {
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int data;
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struct Node* next;
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};
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void push(struct Node** head_ref, int new_data)
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{
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/* allocate node */
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struct Node* new_node = new Node;
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/* put in the data */
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new_node->data = new_data;
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/* link the old list off the new node */
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new_node->next = (*head_ref);
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/* move the head to point to the new node */
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(*head_ref) = new_node;
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}
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bool detectLoop(struct Node* h)
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{
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unordered_set<Node*> s;
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while (h != NULL)
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{
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// If this node is already present
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// in hashmap it means there is a cycle
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// (Because you we encountering the
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// node for the second time).
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if (s.find(h) != s.end())
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return true;
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// If we are seeing the node for
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// the first time, insert it in hash
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s.insert(h);
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h = h->next;
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}
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return false;
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}
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int main()
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{
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/* Start with the empty list */
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struct Node* head = NULL;
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push(&head, 20);
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push(&head, 4);
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push(&head, 15);
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push(&head, 10);
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/* Create a loop for testing */
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head->next->next->next->next = head;
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if (detectLoop(head))
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cout << "Loop found";
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else
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cout << "No Loop";
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return 0;
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}
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