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  1. #include <iostream>
  2. #include <vector>
  3.  
  4. // Definition for singly-linked list.
  5. struct ListNode {
  6.     int val;
  7.     ListNode *next;
  8.     ListNode() : val(0), next(nullptr) {}
  9.     ListNode(int x) : val(x), next(nullptr) {}
  10.     ListNode(int x, ListNode *next) : val(x), next(next) {}
  11. };
  12.  
  13. class Solution {
  14. public:
  15.     ListNode* removeNthFromEnd(ListNode* head, int n) {
  16.         ListNode dummy(0);
  17.         dummy.next = head;
  18.         ListNode* first = &dummy;
  19.         ListNode* second = &dummy;
  20.  
  21.         // Move first n+1 steps ahead
  22.         for (int i = 0; i <= n; ++i) {
  23.             first = first->next;
  24.         }
  25.  
  26.         // Move first to the end, maintaining the gap
  27.         while (first != nullptr) {
  28.             first = first->next;
  29.             second = second->next;
  30.         }
  31.  
  32.         // Skip the desired node
  33.         second->next = second->next->next;
  34.  
  35.         return dummy.next;
  36.     }
  37. };
  38.  
  39.  
  40. ListNode* vectorToList(const std::vector<int>& values) {
  41.     if (values.empty()) return nullptr;
  42.     ListNode* head = new ListNode(values[0]);
  43.     ListNode* current = head;
  44.     for (size_t i = 1; i < values.size(); ++i) {
  45.         current->next = new ListNode(values[i]);
  46.         current = current->next;
  47.     }
  48.     return head;
  49. }
  50.  
  51. std::vector<int> listToVector(ListNode* head) {
  52.     std::vector<int> result;
  53.     while (head != nullptr) {
  54.         result.push_back(head->val);
  55.         head = head->next;
  56.     }
  57.     return result;
  58. }
  59.  
  60. void printList(ListNode* head) {
  61.     while (head != nullptr) {
  62.         std::cout << head->val << " ";
  63.         head = head->next;
  64.     }
  65.     std::cout << std::endl;
  66. }
  67.  
  68. void testRemoveNthFromEnd() {
  69.     Solution solution;
  70.  
  71.     // Test case 1
  72.     ListNode* head1 = vectorToList({1, 2, 3, 4, 5});
  73.     ListNode* result1 = solution.removeNthFromEnd(head1, 2);
  74.     std::vector<int> expected1 = {1, 2, 3, 5};
  75.     std::vector<int> output1 = listToVector(result1);
  76.     std::cout << "Test 1 " << (output1 == expected1 ? "passed" : "failed") << std::endl;
  77.  
  78.     // Test case 2
  79.     ListNode* head2 = vectorToList({1});
  80.     ListNode* result2 = solution.removeNthFromEnd(head2, 1);
  81.     std::vector<int> expected2 = {};
  82.     std::vector<int> output2 = listToVector(result2);
  83.     std::cout << "Test 2 " << (output2 == expected2 ? "passed" : "failed") << std::endl;
  84.  
  85.     // Test case 3
  86.     ListNode* head3 = vectorToList({1, 2});
  87.     ListNode* result3 = solution.removeNthFromEnd(head3, 1);
  88.     std::vector<int> expected3 = {1};
  89.     std::vector<int> output3 = listToVector(result3);
  90.     std::cout << "Test 3 " << (output3 == expected3 ? "passed" : "failed") << std::endl;
  91.  
  92.     // Additional Test case 4
  93.     ListNode* head4 = vectorToList({1, 2, 3, 4, 5});
  94.     ListNode* result4 = solution.removeNthFromEnd(head4, 5);
  95.     std::vector<int> expected4 = {2, 3, 4, 5};
  96.     std::vector<int> output4 = listToVector(result4);
  97.     std::cout << "Test 4 " << (output4 == expected4 ? "passed" : "failed") << std::endl;
  98.  
  99.     // Additional Test case 5
  100.     ListNode* head5 = vectorToList({1, 2, 3});
  101.     ListNode* result5 = solution.removeNthFromEnd(head5, 3);
  102.     std::vector<int> expected5 = {2, 3};
  103.     std::vector<int> output5 = listToVector(result5);
  104.     std::cout << "Test 5 " << (output5 == expected5 ? "passed" : "failed") << std::endl;
  105. }
  106.  
  107. int main() {
  108.     testRemoveNthFromEnd();
  109.     return 0;
  110. }
Success #stdin #stdout 0s 5288KB
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stdin
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Standard input is empty
stdout
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Test 1 passed
Test 2 passed
Test 3 passed
Test 4 passed
Test 5 passed
https://ideone.com/y1eeIB
language:
C++14 (gcc 8.3)
created:
13 hours ago
visibility:
public

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