Debug Using Custom Input

In HackerRank Coding Tests, if your solution is not able to generate the expected output, you can debug your logic using custom input values to locate errors and logical issues. 

The “Test against custom input” option is provided for coding questions using which you can add custom input values to your code and test the output. You can also include the debug print statements in your code to verify the logic.

When you run your program with custom inputs, the Question's test cases are not executed. A custom test case executes your logic using the given input values. The output from your program and any debug outputs are captured and printed.

Example, consider the function to calculate the sum of all elements in an array. Assuming that your logic in the function is not able to produce the expected output, you can debug your logic using custom input values as shown below:

 The output returned by your code with the given custom input values is shown below:

 Tip: While debugging, it is also important to check that you are passing the correct format of input to your code and returning the output in the exact expected format. If Sample Test cases are available for your coding question, download the Sample Test Cases and view the sample input and output files to understand the expected input value and the output from your code.

In some cases, to help you to understand the expected output for the problem, your test setter may have included a hidden solution in the Question. In this scenario, the Expected Output area displays the correct output from the hidden solution for the given custom input values.

In the following example, the problem contains the hidden solution to calculate the sum of two integers. The Expected Output value is displayed from the hidden solution for the given custom input value.

 Note: The solutions to all HackerRank library questions are uploaded. Therefore, candidates can compare their output with the expected output when they add the input to test their code for these questions.

There are two methods of entering the custom input to debug the code:

Raw Format

The candidates have to enter the input in a particular format to test their code. Consider the following example:

Integer Arrays

Problem statement: For the given array of integers, write a function ArraySum to return the sum of its elements. The given function is Int ArraySum(int N), and you must complete this function to return the sum of the elements in a given array.

1. The Function name, ArraySum.
2. The function returns an INTEGER value.
3. The function input is an INTEGER variable N.
   
   

While using custom input for this function to enter the elements of the array, be aware of the input format. For an input array of length Y, the custom input must contain (Y + 1) lines.

The first value in your custom input must specify the length of the array, followed by the equal number of array elements. For example, for the input array [10, 20, 30, 40, 50] and integer n= 123, the test case's input that a candidate requires to enter is:

5
10
20
30
40
50
123

The test case's output would be the sum of the elements: 150. 

Visual Format

The raw format of custom input is not ideal for longer inputs. The visual method is more intuitive and makes it easier for the candidates to enter input. The candidates do not necessarily need to understand or follow a particular format for entering input test cases in this method. They do not need to enter the size of the array. They are required to enter the elements of the array to calculate the output.

Currently, integer, long, string, float, integer array, and string array are supported return types for the visual format of the test case input.

The visual format also makes it easier to input more than one string arrays.

For example: 

If the candidates have to enter two arrays {“chicago”, “austin”, “california”}, {“bangalore”, “delhi”, “chennai”), then the first element to be entered is the size of the array followed by the elements of the array. The input in this case in the raw format is: 

3
Chicago
Austin
California
3
Bangalore
Delhi
Chennai

However, for the visual format, there are different fields for each array and the candidates can just enter the values of the array. They do not need to enter the size of the array. The following screenshot displays the input in visual format:

The following screenshot displays your output and expected output for the test case input provided.

The output from the custom input values

 Note: The Test against custom input option is available for debugging only if your test setter has permitted this option in your Test.