从文本文件读入数组

Question

Hi im currently trying to do a hackerearth challenge sum of medians and it involves me reading from a text file and storing the values in an array. The first value has to be stored in a variable N which i am able to do but the the remaining values have to be stored in an array. This is where i become stuck. i have to read each value line by line and then store it in the array . this is my code that i have been trying to get it working on but i just cant see where im going wrong.

import java.io.BufferedReader; 
import java.io.InputStreamReader; 

class TestClass { 
 public static void main(String args[] ) throws Exception { 

 // read number of data from system standard input. 
 BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); 
 String line = br.readLine(); 
 int N = Integer.parseInt(line); 
 int i = 1;
 int[] myIntArray = new int[N];
  // median sum 
 long SumMedians = 0; 
 int median = 0;


 while (i<N)

     //read one line file and parse as an integer
     //store the value in an array
 { 

     myIntArray [i] = Integer.parseInt(line);

 i = i + 1; // increment i so i is the total numbers read
 }

so as i said i must increment through the text file storing each value on the line in an array. Any help would be amazing thanks

The text file will look like this

5

10

5

1

2

15

one string per line, which i have to pass into an integer. what i will be doing is after i store the value from the line into the array i will be sorting it and finding its medium and then repeat this process until all the values from the text file have been read.

The problem which i am trying to do is this one

http://www.hackerearth.com/problem/algorithm/sum-of-medians-1/

Answer 1

If you're reading from a text file (and not from standard input which is what you're doing at the moment) then you want something like:

// Warning: this could fail if the filename is invaild.
BufferedReader br = new BufferedReader(new FileReader("inputFileName.txt"));

To then read in each line, you can use the following in the while loop:

// Warning: this will crash the program if the line contains anything other than integers.
myIntArray[i] = Integer.parseInt(br.readLine())
 i = i + 1; // increment i so i is the total numbers read

You should also close the reader at the end:

try{
  br.close();
} catch (IOException e)
{
  System.out.println("Error, program exit!");
  System.exit(1);
}

The import should be swapped from import java.io.InputStreamReader to: import java.io.FileReader

Answer 2

由于您只读取1行，因此我怀疑它是由冒号/分号或其他字符分隔的一行。尝试查看StringTokenizer和Scanner类

Answer 3

N = the number from parsing a string to a number In the first part of your program it N = 5

Why are you using while(i<5)?

If anything you should be

r = number of lines in text file;

while (i< r)
{

readline;

parseline;

store in array;

}

and then sort

Answer 4

Adapting the example they gave you

import java.io.BufferedReader;
import java.io.InputStreamReader;

class TestClass {
    public static void main(String args[] ) throws Exception {
        /*
         * Read input from stdin and provide input before running
         */

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        int N = Integer.parseInt(line);

        //create storage array
        int[] myIntArray = new int[N];

        //read remainder of file
        for (int i = 0; i < N; i++) {
            String line = br.readLine();
            myIntArray[i] = Integer.parseInt(line);
        }
        // close file
        br.close();


        //Perform median calculations
        int median = 0;
        ...
        System.out.println(median);
}

}