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  1. import java.util.*;
  2. import java.io.*;
  3.  
  4. public class Main {
  5. 	static BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
  6. 	static BufferedWriter bw=new BufferedWriter(new OutputStreamWriter(System.out));
  7. 	static StringBuilder sb=new StringBuilder();
  8. 	static int front=-1;
  9. 	static int rear=-1;
  10. 	static int[] queue;
  11.  
  12. 	public static void main(String args[]) throws Exception {
  13. 		int num=Integer.parseInt(br.readLine());
  14. 		if(num<1||num>2000000) return;
  15. 		queue=new int[num];
  16. 		for(int i=0;i<num;i++) {
  17. 			String str=br.readLine();
  18. 			switch(str) {
  19. 			case "pop":
  20. 				sb.append(pop()+"\n");
  21. 				break;
  22. 			case "size":
  23. 				sb.append(size()+"\n");
  24. 				break;
  25. 			case "empty":
  26. 				sb.append(empty()+"\n");
  27. 				break;
  28. 			case "front":
  29. 				sb.append(front()+"\n");
  30. 				break;
  31. 			case "back":
  32. 				sb.append(back()+"\n");
  33. 				break;
  34. 			default:
  35. 				if(str.startsWith("push")) {
  36. 					int temp=str.charAt(5)-'0';
  37. 					if(temp<1||temp>100000) return;
  38. 					push(temp);
  39. 				}
  40. 			}
  41. 		}
  42. 		System.out.println(sb);
  43. 	}
  44.  
  45. 	public static void push(int num) {
  46. 		queue[++rear]=num;
  47. 	}
  48.  
  49. 	public static int pop() {
  50. 		if(rear>front) return queue[++front];
  51. 		else return -1;
  52. 	}
  53.  
  54. 	public static int size() {
  55. 		return rear-front;
  56. 	}
  57.  
  58. 	public static int empty() {
  59. 		if(size()<=0) return 1;
  60. 		else return 0;
  61. 	}
  62.  
  63. 	public static int front(){
  64. 		if(size()<=0) return -1;
  65. 		else return queue[front+1];
  66. 	}
  67.  
  68. 	public static int back() {
  69. 		if(size()<=0) return -1;	
  70. 		else return queue[rear];
  71. 	}
  72.  
  73. }
  74.  
  75.  
  76.  
  77.  
  78.  
  79.  
  80.  
  81.  
Success #stdin #stdout 0.08s 34092KB
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https://ideone.com/hZB9mC
language:
Java (HotSpot 12)
created:
3 years ago
visibility:
public

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