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  1. #include <iostream>
  2. #include <bits/stdc++.h>
  3. #include <string>
  4. using namespace std;
  5.  
  6.  
  7. class Node {
  8. 	public:
  9.         int value;
  10.         Node* next;
  11.  
  12.         Node(int a) {
  13.         	value = a;
  14.             next = nullptr;
  15.         }
  16. };
  17.  
  18.  
  19. class ForwardList {
  20. 	public:
  21. 		Node* head;
  22. 		Node* tail; // последний элемент
  23.  
  24. 		ForwardList() {
  25. 			head = nullptr;
  26. 			tail = nullptr;
  27. 		}
  28.  
  29. 		~ForwardList() {
  30. 			while (head != nullptr) pop_front();
  31. 		}
  32.  
  33. 		void pop_front() {
  34. 			if (head == NULL) return;
  35.  
  36. 			if (head == tail) {
  37. 				delete head;
  38. 				head = tail = nullptr;
  39.  
  40. 				return;
  41. 			}
  42.  
  43. 			Node* for_delete = head;
  44. 			head = for_delete->next;
  45. 			delete for_delete;
  46. 		}
  47.  
  48. 		Node* get_at(int x) {
  49. 			if (x < 0) {return nullptr;}
  50.  
  51. 			int n = 0;
  52. 			Node* pointer = head;
  53.  
  54. 			while (n < x && pointer->next)
  55. 			{
  56. 				pointer = pointer->next;
  57. 				n++;
  58. 			}
  59.  
  60. 			return (n == x) ? pointer : nullptr;
  61. 		}
  62.  
  63. 		void push_at(int x, int y) {
  64. 			Node* previous = get_at(x);
  65. 			Node* current = get_at(x + 1);
  66.  
  67. 			Node* new_node = new Node(y);
  68.  
  69. 			if (previous) {
  70. 				previous->next = new_node;
  71.  
  72. 				if (current) {new_node->next = current;}
  73. 			} 
  74.  
  75.  
  76. 			if (head == nullptr) {head = tail = new_node;}
  77. 			if (tail == nullptr) {tail = new_node;}
  78. 		}
  79.  
  80. 		void pop_at(int x) {
  81. 			Node* previous = get_at(x - 1);
  82. 			Node* current = get_at(x);
  83.  
  84. 			if (previous) {previous->next = current->next;}
  85.  
  86. 			if (current) {
  87. 				if (head == current) {head == nullptr;}
  88. 				if (tail == current) {tail == nullptr;}
  89. 				delete current;
  90.  
  91. 			}
  92. 		}
  93.  
  94.  
  95. };
  96.  
  97.  
  98. void execute_query(ForwardList& list, int type, int x, int y) {
  99. 	if (type == 1) {
  100. 		list.push_at(x, y);
  101. 	} else if (type == 2) {
  102. 		cout << list.get_at(x) << "\n";
  103. 	} else {
  104. 		list.pop_at(x);
  105. 	}
  106. }
  107.  
  108. int main() {
  109. 	cin.tie(0);
  110. 	ios::sync_with_stdio(false);
  111.  
  112. 	freopen("input.txt", "r", stdin);
  113. 	freopen("output.txt", "w", stdout);
  114.  
  115. 	ForwardList FL;
  116.  
  117. 	int q;
  118. 	cin >> q;
  119.  
  120.  
  121. 	for (int i = 0; i < q; i++) 
  122. 	{
  123. 		string query;
  124. 		getline(cin, query);
  125.  
  126.  
  127. 		int type = (int) (query[0] - '0');
  128. 		execute_query(
  129. 			FL,
  130. 			type,
  131. 			(int) (query[2] - '0'),
  132. 			(type == 1) ? ((int) (query[4] - '0')) : (0)
  133. 		);
  134. 	}
  135.  
  136. 	return 0;
  137. }
Success #stdin #stdout 0.01s 5316KB
comments (?)
stdin
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6
1 0 1
1 1 2
1 2 3
2 0
2 1
2 2
stdout
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Standard output is empty
https://ideone.com/wZ1NFd
language:
C++ (gcc 8.3)
created:
8 hours ago
visibility:
public

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