Remove ipython solutions because the clutter the repository and I like the Python solutions more

other/sudoku.java

@@ -0,0 +1,150 @@
+import java.util.*;
+import javax.swing.*;
+
+import java.io.IOException;
+import java.io.FileReader;
+import java.io.Reader;
+
+class Sudoku {
+
+  int[] fieldValues = new int[81];
+  int[] emptyFields;
+  int currentField;
+
+  void printField() {
+    String fieldOut = "";
+    int i;
+    for(i=0; i<81; i++) {
+      if(i%27 == 0 && i>0) {
+        fieldOut += "\n---------------------\n";
+      }
+      else if(i%9 == 0) {
+        fieldOut += "\n";
+      }
+      else if(i%3 == 0) {
+        fieldOut += "| ";
+      }
+      if(fieldValues[i] != 0) {
+        fieldOut += fieldValues[i] + " ";
+      }
+      else {
+        fieldOut += "  ";
+      }
+    }
+    System.out.println(fieldOut);
+  }
+
+  /** Function asks for an file name which
+   * should contain a sudoku and this sudoku
+   * into fieldValues, Empty fields should
+   * be marked by a '0'
+   */
+  void loadFieldFromFile() {
+    String fileName = "";
+    Reader reader = null;
+    int i = 0;
+
+    fileName = JOptionPane.showInputDialog( "Enter filename" );
+    System.out.println(fileName);
+
+    try
+    {
+      reader = new FileReader (fileName);
+      for ( int c; ( c = reader.read() ) != -1; ) {
+        int v = 0;
+        v = c - (int) '0';
+        if( v >= 0 && v <= 9 ) {
+          fieldValues[i] = v;
+          i++;
+        }
+        if( i > 80 ) break;
+      }
+    }
+    catch ( IOException e) {
+      System.err.println( "Could not open file " + fileName );
+      return;
+    }
+    finally {
+      try { reader.close(); } catch ( Exception e ) { e.printStackTrace(); }
+    }
+
+    System.out.println("File loaded");
+  }
+
+  /** Function checks if "number" may be inserted
+   * in field "index"
+   */
+  boolean isNumberAllowed(int number, int index) {
+    int i = 0, j = 0;
+    /* check col */
+    for(i=index%9; i<81; i+=9) {
+      if(fieldValues[i] == number)
+        return false;
+    }
+    /* check row */
+    for(i=index/9*9; i<(index/9*9+9); i++) {
+      if(fieldValues[i] == number)
+        return false;
+    }
+    /* check field */
+    int lu = (index/9/3*27) + (index%9/3*3); //first index of field
+    for(j = 0; j<3; j++) {
+      for(i = lu+(j*9); i<lu+(j*9)+3; i++) {
+        if(fieldValues[i] == number)
+          return false;
+      }
+    }
+    return true;
+  }
+
+  /** Function trys to solve the current sudoku
+   * using backtracking algorithm
+   */
+  void solveSudoku() {
+    currentField = 0;
+    stepAhead();
+  }
+
+  boolean stepAhead() {
+    if(currentField==81) {
+      return true;
+    }
+
+    if(fieldValues[currentField] != 0) {
+      currentField++;
+      if(stepAhead()) {
+        return true;
+      }
+    }
+    else {
+      for(int i = 1; i<=9; i++) {
+        if(isNumberAllowed(i, currentField)) {
+          fieldValues[currentField] = i;
+          currentField++;
+          if(stepAhead())
+            return true;
+        }
+      }
+      fieldValues[currentField] = 0;
+    }
+    currentField--;
+
+    return false;
+  }
+
+}
+
+/** This class is to test the
+ * Sudoku class and it's functions
+ */
+class SudokuDemo {
+  public static void main(String[] args) {
+    System.out.println("Sudoku demo loading...");
+    Sudoku s = new Sudoku();
+    s.loadFieldFromFile();
+    s.printField();
+    //s.testAllowed();
+    s.solveSudoku();
+    s.printField();
+  }
+}