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  1. #include <iostream>
  2. #include <unordered_map>
  3. using namespace std;
  4.  
  5. struct Node {
  6.     int data;
  7.     Node* next;
  8. };
  9.  
  10. void removeSingles(Node* head) {
  11.     unordered_map<int, int> count;
  12.     Node* curr = head;
  13.     while (curr != nullptr) {
  14.         count[curr->data]++;
  15.         curr = curr->next;
  16.     }
  17.  
  18.     curr = head;
  19.     Node* prev = nullptr;
  20.     while (curr != nullptr) {
  21.         if (count[curr->data] == 1) {
  22.             if (prev == nullptr) {
  23.                 head = curr->next;
  24.                 delete curr;
  25.                 curr = head;
  26.             } else {
  27.                 prev->next = curr->next;
  28.                 delete curr;
  29.                 curr = prev->next;
  30.             }
  31.         } else {
  32.             prev = curr;
  33.             curr = curr->next;
  34.         }
  35.     }
  36. }
  37.  
  38. void printList(Node* head) {
  39.     Node* curr = head;
  40.     while (curr != nullptr) {
  41.         cout << curr->data << " ";
  42.         curr = curr->next;
  43.     }
  44.     cout << endl;
  45. }
  46.  
  47. int main() {
  48.     Node* head = new Node{1, new Node{2, new Node{3, new Node{2, new Node{4, new Node{5, nullptr}}}}}};
  49.     printList(head);
  50.     removeSingles(head);
  51.     printList(head);
  52.     return 0;
  53. }
  54.  
Success #stdin #stdout 0.01s 5432KB
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https://ideone.com/XwWr34
language:
C++14 (gcc 8.3)
created:
1 year ago
visibility:
public

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