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  1. #include <iostream>
  2. #include <vector>
  3. using namespace std;
  4.  
  5. // Node structure for doubly linked list
  6. struct Node {
  7.     int data;
  8.     Node* next;
  9.     Node* prev;
  10.     Node(int x) : data(x), next(nullptr), prev(nullptr) {}
  11. };
  12.  
  13. class Solution {
  14. public:
  15.     Node* constructDLL(vector<int>& arr) {
  16.         if(arr.empty()) return nullptr;
  17.  
  18.         Node* head = new Node(arr[0]);
  19.         Node* prev = nullptr;
  20.         Node* current = head;
  21.  
  22.         for(int i = 1; i < arr.size(); i++) {
  23.             current->next = new Node(arr[i]);
  24.             current->next->prev = current;
  25.             current = current->next;
  26.         }
  27.  
  28.         return head;
  29.     }
  30. };
  31.  
  32. // Helper function to print DLL forward
  33. void printForward(Node* head) {
  34.     Node* current = head;
  35.     while(current) {
  36.         cout << current->data;
  37.         if(current->next) cout << " <-> ";
  38.         current = current->next;
  39.     }
  40.     cout << endl;
  41. }
  42.  
  43. // Helper function to print DLL backward
  44. void printBackward(Node* tail) {
  45.     Node* current = tail;
  46.     while(current) {
  47.         cout << current->data;
  48.         if(current->prev) cout << " <-> ";
  49.         current = current->prev;
  50.     }
  51.     cout << endl;
  52. }
  53.  
  54. // Helper function to delete DLL
  55. void deleteDLL(Node* head) {
  56.     while(head) {
  57.         Node* temp = head;
  58.         head = head->next;
  59.         delete temp;
  60.     }
  61. }
  62.  
  63. int main() {
  64.     Solution sol;
  65.  
  66.     // Test Case 1: Normal case
  67.     vector<int> arr1 = {1, 2, 3, 4, 5};
  68.     Node* dll1 = sol.constructDLL(arr1);
  69.     cout << "Test 1 - Forward: ";
  70.     printForward(dll1);
  71.  
  72.     // Get tail to test backward traversal
  73.     Node* tail1 = dll1;
  74.     while(tail1->next) tail1 = tail1->next;
  75.     cout << "Test 1 - Backward: ";
  76.     printBackward(tail1);
  77.     deleteDLL(dll1);
  78.  
  79.     // Test Case 2: Single element
  80.     vector<int> arr2 = {10};
  81.     Node* dll2 = sol.constructDLL(arr2);
  82.     cout << "\nTest 2 - Forward: ";
  83.     printForward(dll2);
  84.     cout << "Test 2 - Backward: ";
  85.     printBackward(dll2);  // Same as forward for single node
  86.     deleteDLL(dll2);
  87.  
  88.     // Test Case 3: Empty list
  89.     vector<int> arr3 = {};
  90.     Node* dll3 = sol.constructDLL(arr3);
  91.     cout << "\nTest 3 - Empty list: ";
  92.     printForward(dll3);  // Should print nothing
  93.     deleteDLL(dll3);
  94.  
  95.     return 0;
  96. }
Success #stdin #stdout 0.01s 5288KB
comments (?)
stdin
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Standard input is empty
stdout
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Test 1 - Forward: 1 <-> 2 <-> 3 <-> 4 <-> 5
Test 1 - Backward: 5 <-> 4 <-> 3 <-> 2 <-> 1

Test 2 - Forward: 10
Test 2 - Backward: 10

Test 3 - Empty list:
https://ideone.com/k8rbaK
language:
C++14 (gcc 8.3)
created:
13 days ago
visibility:
public

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