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  1. import java.io.*;
  2. import java.util.*;
  3. import java.math.*;
  4. class Main {
  5.   final static String filename = "renritsu.txt";
  6.   public static void main(String args[]){
  7.     System.out.println("start.");
  8.     double[][] A = null;
  9.  
  10.     //read from data
  11.     try {
  12.       BufferedReader br = new BufferedReader(new FileReader(filename));
  13.       String s;
  14.       String[] vals;
  15.       int rows = 0, cols = 0;
  16.       while((s = br.readLine()) != null){
  17.         vals = s.split(" ");
  18.         cols = Math.max(cols, vals.length);
  19.         rows++;
  20.       }
  21.       System.out.println(rows+"×"+cols+" array found");
  22.       A = new double[rows][cols];
  23.       br.close();
  24.  
  25.       br = new BufferedReader(new FileReader(filename));
  26.       rows = cols = 0;
  27.       while((s = br.readLine()) !=null){
  28.         vals =s.split(" ");//split the line with space
  29.         cols = vals.length;
  30.         for(int i=0; i<cols;i++)
  31.           A[rows][i]=Double.parseDouble(vals[i]);
  32.         rows++;
  33.       }
  34.     } catch (IOException e){
  35.       System.out.println(e);
  36.     }
  37.     dump(A);
  38.  
  39.     //forward
  40.     for(int i = 0; i< A.length ;i++) {
  41.       double P = A[i][i];//pivot
  42.       for(int j = 0; j < A[i].length; j++)
  43.         A[i][j] /= P;
  44.       for (int j = i + 1; j < A.length; j++) {
  45.         P = A[j][i];
  46.         if (Math.abs(P) > 0.0001) {
  47.           for(int k = 0; k < A.length; k++) {
  48.             double v = A[k][i];
  49.             A[j][k] /= P;
  50.             A[j][k] -= A[i][k];
  51.           }
  52.         }
  53.       }
  54.     }
  55.     dump(A);
  56.  
  57.     //backward
  58.     for(int i = A.length - 1; i >= 0; i--)
  59.       for (int j = i - 1; j >= 0; j--) {
  60.         A[j][A.length] -= A[j][A.length] * A[j][i];
  61.         A[j][i] = 0.0;
  62.       }
  63.     dump(A);
  64.   }
  65.   static void dump(double[][] a) {
  66.     for(int i = 0; i < a.length; i++) {
  67.       for(int j = 0; j < a[i].length; j++)
  68.         System.out.printf("%6.3f ", a[i][j]);
  69.       System.out.println();
  70.     }
  71.     System.out.println();
  72.   }
  73. }
  74. /* end */
  75.  
Runtime error #stdin #stdout 0.02s 245632KB
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Standard input is empty
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start.
java.io.FileNotFoundException: renritsu.txt (No such file or directory)
https://ideone.com/bbtHJ
language:
Java (HotSpot 12)
created:
12 years ago
visibility:
public

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