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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. struct ListNode {
  5.     int val;
  6.     ListNode *next;
  7.     ListNode() : val(0), next(nullptr) {}
  8.     ListNode(int x) : val(x), next(nullptr) {}
  9.     ListNode(int x, ListNode *next) : val(x), next(next) {}
  10. };
  11. void printList(ListNode* head) {
  12.     while (head) {
  13.         cout << head->val << " ";
  14.         head = head->next;
  15.     }
  16.     cout << endl;
  17. }
  18.  
  19. class Solution {
  20. public:
  21.     ListNode* reverseBetween(ListNode* head, int left, int right) {
  22.         if (!head || left == right) return head;
  23.  
  24.         ListNode dummy(0);
  25.         dummy.next = head;
  26.         ListNode* prev = &dummy;
  27.  
  28.         for (int i = 0; i < left - 1; i++) {
  29.             prev = prev->next;
  30.         }
  31.  
  32.         ListNode* curr = prev->next;
  33.         ListNode* next = nullptr;
  34.  
  35.         cout << "Initial list before reversing: ";
  36.         printList(dummy.next);
  37.  
  38.         for (int i = 0; i < right - left; i++) {
  39.             next = curr->next;
  40.             curr->next = next->next;
  41.             next->next = prev->next;
  42.             prev->next = next;
  43.  
  44.             cout << "After iteration " << i + 1 << ": ";
  45.             printList(dummy.next);
  46.         }
  47.  
  48.         return dummy.next;
  49.     }
  50. };
  51.  
  52.  
  53.  
  54. int main() {
  55.     ListNode* head = new ListNode(1);
  56.     head->next = new ListNode(2);
  57.     head->next->next = new ListNode(3);
  58.     head->next->next->next = new ListNode(4);
  59.     head->next->next->next->next = new ListNode(5);
  60.  
  61.     int left = 2, right = 4;
  62.     Solution sol;
  63.     head = sol.reverseBetween(head, left, right);
  64.  
  65.     cout << "Final reversed list: ";
  66.     printList(head);
  67.  
  68.     return 0;
  69. }
  70.  
Success #stdin #stdout 0.01s 5288KB
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stdin
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Standard input is empty
stdout
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Initial list before reversing: 1 2 3 4 5 
After iteration 1: 1 3 2 4 5 
After iteration 2: 1 4 3 2 5 
Final reversed list: 1 4 3 2 5
https://ideone.com/wrakYK
language:
C++ (gcc 8.3)
created:
12 days ago
visibility:
public

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