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  1. import java.util.*;
  2. import java.lang.*;
  3. import java.io.*;
  4.  
  5. class Main {
  6. 	public static class Node {
  7. 		public int value;
  8. 		public Node next;
  9.  
  10. 		public Node() {
  11. 			value = 0;
  12. 			next = null;
  13. 		}
  14. 		public Node(int newValue, Node newNext) {
  15. 			value = newValue;
  16. 			next = newNext;
  17. 		}
  18. 	}
  19.  
  20. 	public static class Queue {
  21. 		private int size;
  22. 		private Node first;
  23. 		private Node last;
  24.  
  25. 		public Queue() {
  26. 			size = 0;
  27. 			first = null;
  28. 			last = null;
  29. 		}
  30.  
  31. 		public void push(int v) {
  32. 			Node newNode = new Node(v, null);
  33. 			if (size == 0) {
  34. 				first = last = newNode;
  35. 			} else {
  36. 				last.next = newNode;
  37. 				last = newNode;
  38. 			}
  39. 			size++;
  40. 		}
  41. 		public boolean pop() {
  42. 			boolean ret = false;
  43. 			if (size > 0) {
  44. 				int val = first.value;
  45. 				first = first.next;
  46. 				size--;
  47. 				System.out.print(val);
  48. 				ret = true;
  49. 			}
  50. 			return ret;
  51. 		}
  52. 		public boolean front() {
  53. 			boolean ret = false;
  54. 			if (size > 0) {
  55. 				System.out.print(first.value);
  56. 				ret = true;
  57. 			}
  58. 			return ret;
  59. 		}
  60. 		public int getSize() {
  61. 			return size;
  62. 		}
  63. 		public void clear() {
  64. 			first = null;
  65. 			last = null;
  66. 			size = 0;
  67. 		}
  68. 	}
  69. 	public static void main(String[] args) {
  70. 		Queue q = new Queue();
  71. 		String s;
  72. 		int n;
  73. 		Scanner scan = new Scanner(System.in);
  74. 		while ((s = scan.next()) != null) {
  75. 			switch(s) {
  76. 				case "size": System.out.println(q.getSize()); break;
  77. 				case "push":
  78. 					n = scan.nextInt();
  79. 					q.push(n);
  80. 					System.out.println("ok");
  81. 					break;
  82. 				case "pop":
  83. 					if (q.pop() == false) {
  84. 						System.out.print("error");
  85. 					}
  86. 					System.out.println();
  87. 					break;
  88. 				case "front":
  89. 					if (q.front() == false) {
  90. 						System.out.print("error");
  91. 					}
  92. 					System.out.println();
  93. 					break;
  94. 				case "clear":
  95. 					q.clear();
  96. 					System.out.println("ok");
  97. 					break;
  98. 				case "exit":
  99. 					System.out.println("bye");
  100. 					return;
  101. 				default: break;
  102. 			}
  103. 		}
  104. 	}
  105. }
Success #stdin #stdout 0.06s 711680KB
comments (?)
stdin
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size
push 1
size
push 2
size
push 3
size
exit
stdout
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0
ok
1
ok
2
ok
3
bye
https://ideone.com/3heNRA
language:
Java (HotSpot 12)
created:
8 years ago
visibility:
secret

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