Karel Top — Codehs All Answers

Karel is patient, but the autograder is not. If Karel spins in circles forever, your browser freezes.

Problem: The world is filled with balls. Remove all of them. Solution:

function main() 
    while (leftIsClear()) 
        cleanRow();
        moveUpAndReverse();
cleanRow();
function cleanRow() 
    while (frontIsClear()) 
        safeTakeBall();
        move();
safeTakeBall();
function moveUpAndReverse() 
    turnLeft();
    move();
    turnLeft();

Problem: Karel starts at the bottom of a staircase with 5 steps. Write a program to make Karel climb the staircase.

Solution:

function start() 
  var i;
  for (i = 0; i < 5; i++) 
    move();
    turnLeft();
    move();
    turnRight();

Task: Define a start() function to stack pancakes. codehs all answers karel top

def start():
    move()
    make_pancakes()
    move()
def make_pancakes():
    putBall()
    putBall()
    putBall()

The Goal: Karel builds "hospitals" (rectangles of balls) over piles of supplies.

Solution:

public class HospitalKarel extends Karel 
    public void run() 
        while(frontIsClear()) 
            if(ballsPresent()) 
                makeHospital();
move();
// Check the last corner
        if(ballsPresent()) 
            makeHospital();
private void makeHospital() 
    // Logic to build the hospital structure
    turnLeft();
    move();
    putBall();
    turnRight();
    move();
    putBall();
    turnRight();
    move();
    putBall();
    turnAround();
    move();
    move();
    turnLeft();

Problem: Make Karel move forward 10 times.

Solution:

function start() 
  for (var i = 0; i < 10; i++) 
    move();

Before diving into specific answers, you must master these 5 helper functions. They appear in every "top" solution.

// Standard movement
function moveToWall() 
    while (frontIsClear()) 
        move();
// The classic turnaround
function turnAround() 
turnLeft();
turnLeft();
 Karel is patient, but the autograder is not
// Right turn (CodeHS doesn't have turnRight by default)
function turnRight() 
turnLeft();
turnLeft();
turnLeft();

// Put a ball if none exists
function safePutBall() 
if (noBallsPresent()) 
putBall();

// Safe pick up
function safeTakeBall() 
if (ballsPresent()) 
takeBall();