Data commit

Task/Kaprekar-numbers/Java/kaprekar-numbers.java

@@ -0,0 +1,31 @@
+public class Kaprekar {
+    private static String[] splitAt(String str, int idx){
+        String[] ans = new String[2];
+        ans[0] = str.substring(0, idx);
+        if(ans[0].equals("")) ans[0] = "0"; //parsing "" throws an exception
+        ans[1] = str.substring(idx);
+        return ans;
+    }
+
+    public static void main(String[] args){
+        int count = 0;
+        int base = (args.length > 0) ? Integer.parseInt(args[0]) : 10;
+        for(long i = 1; i <= 1000000; i++){
+            String sqrStr = Long.toString(i * i, base);
+            for(int j = 0; j < sqrStr.length() / 2 + 1; j++){
+                String[] parts = splitAt(sqrStr, j);
+                long firstNum = Long.parseLong(parts[0], base);
+                long secNum = Long.parseLong(parts[1], base);
+                //if the right part is all zeroes, then it will be forever, so break
+                if(secNum == 0) break;
+                if(firstNum + secNum == i){
+                    System.out.println(i + "\t" + Long.toString(i, base) +
+                            "\t" + sqrStr + "\t" + parts[0] + " + " + parts[1]);
+                    count++;
+                    break;
+                }
+            }
+        }
+        System.out.println(count + " Kaprekar numbers < 1000000 (base 10) in base "+base);
+    }
+}