【CodeChef】Enormous Input Test

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The purpose of this problem is to verify whether the method you are using to read input data is sufficiently fast to handle problems branded with the enormous Input/Output warning. You are expected to be able to process at least 2.5MB of input data per second at runtime.

Input

The input begins with two positive integers n k (n, k<=10⁷). The next n lines of input contain one positive integer t_i, not greater than 10⁹, each.

Output

Write a single integer to output, denoting how many integers t_i are divisible by k.

题解：记录这道题主要是为了记录java中Scanner和BufferReader的区别，开始用Scanner，效率非常低，所以就TLE了。根据StackOverFlow里面解释：BufferReader只是从流中读入数据，但不对数据做任何处理，Scanner按照需求解析数据并读入，比如nextInt(),nextDouble()等。更详细的答案还有这里。

总结一下：

• A BufferedReader is a simple class meant to efficiently read from the underling stream.
•  BufferedReader is synchronized, so read operations on a BufferedReader can safely be done from multiple threads.
• Scanner can parse the underlying stream for primitive types and strings using regular expressions.
• A scanner however is not thread safe, it has to be externally synchronized.

对于原文中的“ A scanner can do all that a BufferedReader can do and at the same level of efficiency as well.”不太认同，因为通过OJ来看，BufferReader的效率确实比Scanner高。

BufferReader的用法就用这道题的AC代码记录：

 1 import java.io.BufferedReader;
 2 import java.io.IOException;
 3 import java.io.InputStreamReader;
 4 
 5 public class Main {
 6 
 7     public static void main(String[] args) {
 8         // TODO Auto-generated method stub
 9         BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
10         try{
11             String[] line =(bf.readLine()).split(" ");
12             int n = Integer.parseInt(line[0]);
13             int k = Integer.parseInt(line[1]);
14             int count = 0;
15             while(n-- > 0){
16                 int num = Integer.parseInt(bf.readLine());
17                 if(num%k == 0)
18                     ++count;
19             }
20             System.out.println(count);
21         }
22         catch(IOException e){
23             System.out.print("input error");
24         }
25     }
26 
27 }

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【CodeChef】Enormous Input Test

标签：style   blog   http   color   java   os   strong   io   

原文地址：http://www.cnblogs.com/sunshineatnoon/p/3881145.html