Recursion Pepper

Another way to loop Call yourself repeatedly until you say to stop. Example: add up 10 numbers using addUp. -- Input – number to count -- Ouput – total of all those numbers added up Logic: If the number I am counting is 0, just return 0. If the number I am counting is anything else, return the number I have + the total of all the rest (the number I have – 1) Requires: Trust the function will do its job A stopper A way to reach the stopper (decrement or increment) Code the addUp method and call it to addUp(10)

addUp Solution public class AddUp { public static void main() System.out.println(addUp(10)); } public static int addUp(int numberToCount) if (numberToCount == 0) return numberToCount;} else return numberToCount + addUp(numberToCount-1);

Create a string of stars starString routine -- Input – number of stars needed -- Ouput – String of that many stars Logic: If the number I am counting is 1, just return 1 star. If the number I am counting is anything else, return one star + all the rest of the stars (the number I have – 1) Requires: Trust the function will do its job A stopper A way to reach the stopper (decrement or increment) Code the starString method and call it to create starString(10)

String of Stars public static String starString (int numberStars) { if (numberStars == 0) return(""); } else return "*" + starString(numberStars-1);

Work with shapes Divide a rectangle up 4 levels deep First print 1 big square Then divide that one square Test fully Then create another method to printInsideSquares with input: level, paintbrush, starting x,y and size. Stop at level 1 – just print the square with no division At every other level, print a big square and printInsideSquares for the smaller squares

Work with Shapes First hint: Here is how to draw 1 level of 4 squares inside 1 square: public static void printOneInsideSquares(int level, Graphics g, int x, int y, int size) { g.drawRect(x,y,size,size); g.drawRect( x,y,size/2,size/2); // top left g.drawRect( x+(size/2), y,size/2,size/2); // top right g.drawRect( x,y+size/2,size/2,size/2); // bottom left g.drawRect( x+size/2,y+size/2,size/2,size/2); // bottom right } Now – add the level logic: stopper: If level == 1, just draw the main rectangle do a job and call itself to do the rest: If level higher, draw main rectangle and printInsideSquares of the small squares at the next level.