// CSE 143, Summer 2016
// This file contains several examples of recursive definitions.

import java.io.*;
import java.util.*;

public class Recurse {
  public static void main(String[] args) throws FileNotFoundException {
    writeStars(8);
    writeStars2(6);
    Scanner input = new Scanner(new File("input.txt"));
    reverse(input);
    System.out.println(stutter(-348));
    System.out.println(stutter2(-348));
    System.out.println(stutter(1056));
    System.out.println(stutter2(1056));
  }

  // iterative method that produces an output line of exactly n stars
  public static void writeStars(int n) {
    for (int i = 0; i < n; i++) {
      System.out.print("*");
    }
    System.out.println();
  }

  // recursive method that produces an output line of exactly n stars
  public static void writeStars2(int n) {
    if (n == 0) {
      System.out.println();
    } else {
      System.out.print("*");
      writeStars2(n - 1);
    }
  }

  // post: reads a file, writing the lines to System.out in reverse order
  public static void reverse(Scanner input) {
    if (input.hasNextLine()) {
      // recursive case
      String line = input.nextLine();
      reverse(input);
      System.out.println(line);
    }
    // implicit base case
  }

  // returns the integer obtained by replacing every digit of n with two of
  // that digit.  For example, stutter(348) returns 334488.
  public static int stutter(int n) {
    // here's the longer version of stutter
    if (n < 0) {
      return -stutter(-n);
    } else if (n / 10 == 0) {
      // base case
      return 10 * n + n;
    } else {
      // recursive case
      int digit = n % 10;
      int theRest = n / 10;
      theRest = stutter(theRest);
      return 100 * theRest + 10 * digit + digit;
    }
  }

  public static int stutter2(int n) {
    // here's the short ninja version
    if (n < 0) {
      return -stutter(-n);
    } else if (n / 10 == 0) {
      // base case
      return 10 * n + n;
    } else {
      return 100 * stutter(n / 10) + stutter(n % 10);
    }
  }
}