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  1. #include <list>
  2. #include <iostream>
  3. using namespace std;
  4.  
  5. // Function to find the intersection of two sorted lists
  6. std::list<int> intersection(const std::list<int>& l1, const std::list<int>& l2) {
  7.     std::list<int> result; // Stores the common elements
  8.     auto it1 = l1.begin(); // Iterator for l1
  9.     auto it2 = l2.begin(); // Iterator for l2
  10.  
  11.     // Traverse both lists using iterators
  12.     while (it1 != l1.end() && it2 != l2.end()) {
  13.         if (*it1 < *it2) {
  14.             ++it1; // Move iterator of l1 forward
  15.         } else if (*it2 < *it1) {
  16.             ++it2; // Move iterator of l2 forward
  17.         } else { 
  18.             // Both elements are equal, add to result
  19.             result.push_back(*it1);
  20.             ++it1;
  21.             ++it2;
  22.         }
  23.     }
  24.     return result; // Return the intersection list
  25. }
  26.  
  27. // Function to print a list
  28. void printList(const std::list<int>& lst) {
  29.     std::cout << "{ ";
  30.     for (int num : lst) {
  31.         std::cout << num << " ";
  32.     }
  33.     std::cout << "}" << std::endl;
  34. }
  35.  
  36. // Main function
  37. int main() {
  38.     // Test Case 1: {1, 2, 3, 4} ∩ {2, 3} = {2, 3}
  39.     std::list<int> l1 = {1, 2, 3, 4};
  40.     std::list<int> l2 = {2, 3};
  41.     std::list<int> result1 = intersection(l1, l2);
  42.  
  43.     std::cout << "Test Case 1: Intersection: ";
  44.     printList(result1); // Expected Output: {2, 3}
  45.     // Test Case 2: {2, 9, 14} ∩ {1, 7, 15} = {}
  46.     std::list<int> l3 = {2, 9, 14};
  47.     std::list<int> l4 = {1, 7, 15};
  48.     std::list<int> result2 = intersection(l3, l4);
  49.     std::cout << "Test Case 2: Intersection: ";
  50.     printList(result2); // Expected Output: {}
  51.  
  52.     // Test Case 3: Empty list ∩ {2, 3} = {}
  53.     std::list<int> l5;  // Empty list
  54.     std::list<int> l6 = {2, 3};
  55.     std::list<int> result3 = intersection(l5, l6);
  56.  
  57.     std::cout << "Test Case 3 (Empty l1): Intersection: ";
  58.     printList(result3); // Expected Output: {}
  59.  
  60.     return 0;
  61. }
  62.  
Success #stdin #stdout 0.01s 5284KB
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stdin
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Standard input is empty
stdout
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Test Case 1: Intersection: { 2 3 }
Test Case 2: Intersection: { }
Test Case 3 (Empty l1): Intersection: { }
https://ideone.com/TU5ouP
language:
C++ (gcc 8.3)
created:
5 days ago
visibility:
public

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