PLUM HQ | SE3 | Backend | Interview Experience | Jan 2025 | Rejected

Round 1

Questions:

1. Problem 1: Car Fleet
   My solution: Accepted in one go: Submission

2. Problem 2: Course Schedule
   My solution: Accepted in one go: Submission

Candidate's Approach

No approach provided.

Interviewer's Feedback

No feedback provided.

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Round 2

Questions: Problem Statement:
You have a spreadsheet with a maximum of 26 rows and a maximum of 9 columns. The rows are labeled A-Z and the columns are numbered 1-9. Each cell is identified by its row label followed by its column number.

| Spreadsheet | 1 | 2 | 3 | 4 | |-----------|-----------|-----------|-------|-------| | A | 9 | A1 + C2 / D3 | 5 | B4 | | B | 4 | -10 | A3 + D3 | 6 | | C | -23 | 2 | 9 | A1 * B2 | | D | A4 | 0 | -10 | B3 |

Each cell in the spreadsheet either has a value (a decimal number), or a formula which can be used to compute its value. The formula is an expression with the four standard binary operators (+, -, *, /), and operands as either decimal numbers, or other cell identifiers.

Please implement the following in a programming language of your choice

ClassName: Spreadsheet
Constructor:

• Spreadsheet(String[][] spreadsheetCells) : Creates a Spreadsheet where spreadsheetCells[i][j] is the initial expression/value specifying the contents of the cell in the ith row and jth column.

Methods:

• double getValue(string cell): Returns the decimal value of the corresponding cell.

Adding my Code

I find this question really frustrating and not useful to ask in a coding interview. Interviewer neither shared what exactly he is looking for. Is it a problem-solving round or a machine coding round?

I lose interest to solve the problem and thus just did whatever I can to spend 1 hour. (I don't regret what I did).
The below solution is incomplete and just what I implemented.

// Online Java Compiler
// Use this editor to write, compile and run your Java code online

class Main {
    private static double [][] results;
    private static double [][] dp;
    public static void main(String[] args) {
        String[][] sheet = {
            {"9", "A1 + C2 / D3", "5", "B4"},
            {"4", "-10", "A3 + D3", "6"},
            {"-23", "2", "9", "A1 * B2"},
            {"A4", "0", "-10", "B3"}
        };
        initializeResults(sheet);
        System.out.println(getValue("A1"));
        //System.out.println(getValue());
    }
    // Assumptions to skip validations
    // Assuming [A-Z]
    public static double getValue(String cell) {
        return results[getRow(cell)][getCol(cell)];
    }
    private static void initializeResults(String[][] sheet) {
        results = new double[26][9];
        int rows = sheet.length;
        int cols = sheet[0].length;
        // dp = new double[rows][cols];
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                results[i][j] = evaluate(sheet[i][j]);
            }
        }
    }
    private static String[] precedence = {"/", "*", "+", "-"};
    private static double evaluate(String cellVal) {
        String[] ele = cellVal.split(" ");
        if (ele.length == 1) {
            return getVal(ele[0]);
        }
        String[] tempScan = ele;
        for (int i = 0; i < precedence.length; i++) {
            if (tempScan.contains(precedence[i])) {
                tempScan = evaluateOperator(tempScan, precedence[i]);
            }
        }
        return getVal(tempScan[0]);
    }
    private static double getVal(String ele) {
        char c = ele.charAt(0) - '0';
        if (c < '0' || c > '9')
            return evaluate(sheet[getRow(ele)][getCol(ele)]);
        else 
            return Double.parseDouble(ele);
    }
    private static String[] evaluateOperator(String[] ele, String operator) {
        Stack<String> st = new Stack();
        for (int i = 0; i < ele.length; i++) {
            if (ele[i].equals(operator)) {
                double second = getVal(ele[i + 1]);
                double first = st.pop();
                st.add(calculate(first, second, operator));
                i++;
            }
            else if (isOperator(ele[i])) {
                st.add(ele[i]);
            }
            else {
                st.add(getVal(ele[i]));
            }
        }
        // Convert stack to array
        String[] temp = new String[stack.size()];
        for (int i = stack.size() - 1; i >= 0; i--) {
            temp[i] = stack.pop();
        }
        return temp;
    }
    private static boolean isOperator(String ele) {
        if (ele.equals("/") || ele.equals("*") || ele.equals("-") || ele.equals("+")) {
            return true;
        }
        return false;
    }
    private static double calculate(String first, String second, String operator) {
        if (operator.equals("/")) {
            return Double.parseDouble(first) / Double.parseDouble(second);
        }
        if (operator.equals("*")) {
            return Double.parseDouble(first) * Double.parseDouble(second);
        }
        if (operator.equals("+")) {
            return Double.parseDouble(first) + Double.parseDouble(second);
        }
        return Double.parseDouble(first) - Double.parseDouble(second);
    }
    
    private static int getRow(String cell) {
        char c = cell.charAt(0);
        return c - 'A';
    }
    private static int getCol(String cell) {
        char c = cell.charAt(1);
        return c - '1';
    }
}

Candidate's Approach

The candidate expressed frustration with the question, feeling it was not useful for a coding interview. They mentioned that the interviewer did not clarify whether it was a problem-solving or machine coding round, which led to a loss of interest in solving the problem. The provided solution is incomplete and reflects only what the candidate could implement within the time limit.

Interviewer's Feedback

No feedback provided.

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