Convert int array to directions

Question

I have a code snippet (see snippet below) that generates an array like this: [0, 3, 1, -2, 0, -1, 1, 1, -2]. The int numbers here represent movements from one position to another. I would like to have the numerical values translated into text that would represent directions starting from the 0. A Positive number represents the number of steps to the East--so the number 3 would be translated into "eee", the number two would be "ee" and so on. Negative values represents steps in the opposite direct West so that -2 would be displayed as ww, and so on. No movement should be represented as 0.

I'm pretty new to all this and am not sure how the take the values from the array and turn them into the instructions as described above.

The code below shows how the array of integers is generated--subtracting the next location from the previous to get the number of steps between them.

int [] differenceX = new int [noOfRecordsX];
differenceX [0] = 0;

for( int i=0; i < noOfRecordsX -1 ;i++)
{
   differenceX [i+1]= inputX [i+1] - inputX[i];
}

From here I want to generate the text describing the steps in the respective direction so that this array:

[0, 3, 1, -2, 0, -1, 1, 1, -2]

would be transformed to this string:

0,eee,e,ww,0,w,e,e,ww

Answer 1

You can do so by using the following code :

int arr[] = { 0, 3, 1, -2, 0, -1, 1, 1, -2 };

for (int i = 0; i < arr.length; i++) {
    if (arr[i] < 0) { // west
        for (int j = arr[i]; j < 0; j++) {
            System.out.println("w");
        }
    } else if (arr[i] > 0) { // east
        for (int j = 0; j < arr[i]; j++) {
            System.out.println("e");
        }
    }
}

• If the number is negative then we iterate from that value upto 0.
• If the number is positive then we iterate from 0 upto that value.

Answer 2

If you wish to get the string back instead of just writing to the console try this:

private void testMyMethod(){
    String resultString = "";
    int[] array = { 0, 3, 1, -2, 0, -1, 1, 1, -2 };

    for(int step : array){
        String direction = convertToDirection(step);
        // Adding a comma -- as you requested
        // just add this in case you what to indicate a start point ==> X
        if(direction.isEmpty()){
            resultString = resultString.concat("X");
        }
        else{
            resultString = resultString.concat(direction);
        }
        resultString = resultString.concat(",");
    }
    resultString = resultString.subString(0, resultString.length()-1);
    myTextView.setText(resultString);
}

private String convertToDirection(int step){
    String direction = "";

    if(step > 0){
        direction = "e";
    }
    else if(step < 0){
        direction = "w";
    }

    String result = "";
    int len = Math.abs(step);

    for(int i = 0; i < len; i++){
        result = result.concat(direction);
    }

    return result;
}

---

Edit:
A less verbose solution:

private void testMyMethod(){
    int[] array = { 0, 3, 1, -2, 0, -1, 1, 1, -2 };
    StringBuilder sb = new StringBuilder();
    for(int step : array){
        sb.append(convertToDirection(step).concat(","));
    }
    // Remove the last ","
    sb.deleteCharAt(sb.length()-1);
    myTextView.setText(sb.toString());
}

private String convertToDirection(int step){
    if(step == 0) return "0";
    String direction = step > 0 ? "w" : "e";

    int len = Math.abs(step);
    return new String(new char[len]).replace("\0", direction);
}

Borrowing this: new String(new char[len]).replace("\0", direction);
from this solution: Repeat String

Answer 3

We should better use char repeating instead of loops. Look at Simple way to repeat a String in java for different ways.

int arr[] = { 0, 3, 1, -2, 0, -1, 1, 1, -2 };
StringBuilder output = new StringBuilder();
for(int step : array){
    int length = Math.abs(step);
    if (step < 0) { // west
        output.append(new String(new char[length]).replace("\0", "w"));
    } 
    else if (step > 0) { // east
        output.append(new String(new char[length]).replace("\0", "e"));
    }
    else  output.append("0");
}

}