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Calculator with Method Chaining - Solution & Explanation

Easy8 min readAsked at: Microsoft, Bloomberg
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Problem Statement

Design a Calculator class. The class should provide the mathematical operations of addition, subtraction, multiplication, division, and exponentiation. It should also allow consecutive operations to be performed using method chaining. The Calculator class constructor should accept a number which serves as the initial value of result.

Your Calculator class should have the following methods:

  • add - This method adds the given number value to the result and returns the updated Calculator.
  • subtract - This method subtracts the given number value from the result and returns the updated Calculator.
  • multiply - This method multiplies the result  by the given number value and returns the updated Calculator.
  • divide - This method divides the result by the given number value and returns the updated Calculator. If the passed value is 0, an error "Division by zero is not allowed" should be thrown.
  • power - This method raises the result to the power of the given number value and returns the updated Calculator.
  • getResult - This method returns the result.

Solutions within 10-5 of the actual result are considered correct.

 

Example 1:

Input: 
actions = ["Calculator", "add", "subtract", "getResult"], 
values = [10, 5, 7]
Output: 8
Explanation: 
new Calculator(10).add(5).subtract(7).getResult() // 10 + 5 - 7 = 8

Example 2:

Input: 
actions = ["Calculator", "multiply", "power", "getResult"], 
values = [2, 5, 2]
Output: 100
Explanation: 
new Calculator(2).multiply(5).power(2).getResult() // (2 * 5) ^ 2 = 100

Example 3:

Input: 
actions = ["Calculator", "divide", "getResult"], 
values = [20, 0]
Output: "Division by zero is not allowed"
Explanation: 
new Calculator(20).divide(0).getResult() // 20 / 0 

The error should be thrown because we cannot divide by zero.

 

Constraints:

  • actions is a valid JSON array of strings
  • values is a valid JSON array of numbers
  • 2 <= actions.length <= 2 * 104
  • 1 <= values.length <= 2 * 104 - 1
  • actions[i] is one of "Calculator", "add", "subtract", "multiply", "divide", "power", and "getResult"
  • First action is always "Calculator"
  • Last action is always "getResult"

Approach Overview

Problem Overview: Design a calculator object that supports chained arithmetic operations such as add(), subtract(), multiply(), and divide(). Each method updates an internal value and returns the calculator instance so the next operation can be called in the same expression.

Approach 1: Class Design with Method Chaining (O(1) time per operation, O(1) space)

This approach uses a simple class that stores the current numeric value as internal state. Each arithmetic method modifies that value and then returns self (Python) or this (Java). Returning the same object enables chaining: calc.add(5).multiply(2).subtract(3). Internally, each operation performs a constant-time arithmetic update, so the time complexity per call is O(1) and the class only stores one number, giving O(1) space. This pattern is common in object-oriented design and relies on the concept of returning the current instance from methods.

The key insight is that the calculator never creates new objects for each step. Instead, it mutates the stored value and returns the same instance. This keeps the implementation small and efficient while still providing a clean API. Division requires one extra check: if the divisor is zero, throw an exception to prevent invalid state.

Approach 2: Fluent Interface with Error Handling (O(1) time per operation, O(1) space)

A more structured variation follows the fluent interface design pattern. The class still stores the current value, but each method explicitly validates inputs and handles error cases. For example, divide() checks for zero and throws an exception, while other operations simply update the stored value. After validation and calculation, the method returns this so the chain continues.

This approach is common in JavaScript and C# APIs where fluent method calls improve readability and developer ergonomics. The implementation still performs constant-time arithmetic operations and uses constant memory. The difference lies in defensive checks and clearer API design, which is important when building reusable libraries or interview-quality class structures. The design also demonstrates understanding of class design and object-oriented programming patterns.

Recommended for interviews: The standard class with method chaining is what interviewers expect. It shows you understand how returning the current object enables chained calls and how to maintain internal state cleanly. Mentioning the fluent interface pattern and adding divide-by-zero validation demonstrates stronger API design thinking. The brute implementation proves you understand chaining mechanics, while the polished version shows production-level design awareness.

Approach 1: Class Design with Method Chaining

In this approach, we will design a Calculator class with a constructor that initializes the result. Each operation method will modify the object's state and return the Calculator object itself to allow method chaining. The method for division needs to handle division by zero gracefully by throwing an appropriate exception.

In the Python solution, each method modifies self.result, a class attribute, and returns self to allow method chaining. The divide method checks for division by zero and raises a ValueError if encountered. The getResult() method returns the current result.

Code

PythonJava

Python

Java

Complexity

Time Complexity: O(1) for each operation since they all perform a constant amount of work.
Space Complexity: O(1) since we use only a fixed amount of space irrespective of input size.

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Approach 2: Fluent Interface with Error Handling

This approach emphasizes clear error management alongside method chaining. Each mathematical function adjusts the internal result and returns the instance for seamless operation chaining. Special attention is paid to division, where an exception is thrown in case of dividing by zero, ensuring the program handles this gracefully.

In the JavaScript implementation, each operation method updates the result attribute and returns the current instance to enable method chaining. The divide method checks for zero to prevent division by zero, throwing an Error as appropriate. The method getResult retrieves the current value of result.

Code

JavaScriptC#

JavaScript

C#

Complexity

Time Complexity: O(1) for each operation; each involves direct arithmetic with a constant time overhead.
Space Complexity: O(1) due to constant space usage regardless of input size.

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Approach 3: Default Approach

Code

TypeScript

TypeScript

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Complexity Comparison

ApproachComplexity
Class Design with Method Chaining

Time Complexity: O(1) for each operation since they all perform a constant amount of work.
Space Complexity: O(1) since we use only a fixed amount of space irrespective of input size.

Fluent Interface with Error Handling

Time Complexity: O(1) for each operation; each involves direct arithmetic with a constant time overhead.
Space Complexity: O(1) due to constant space usage regardless of input size.

Default Approach—

Detailed Complexity Analysis

ApproachTimeSpaceWhen to Use
Class Design with Method ChainingO(1) per operationO(1)Standard interview solution demonstrating method chaining using self/this
Fluent Interface with Error HandlingO(1) per operationO(1)When building production-style APIs with validation such as divide-by-zero checks

Video Solution

Calculator with Method Chaining | Leetcode 2726 | 30 Days of JavaScript #javascript #leetcode • Learn With Chirag • 1,296 views views

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Frequently Asked Questions

Is Calculator with Method Chaining easy or hard?
Calculator with Method Chaining is categorized as an Easy problem because it mainly tests understanding of classes and method chaining. The implementation is short, and the complexity is constant time and constant space.
Calculator with Method Chaining Python/Java solution
Python implementations return self from each method, while Java implementations return this. Both maintain an internal value field that gets updated after every operation. The chaining behavior works the same in both languages and runs in O(1) time per operation.
How to solve Calculator with Method Chaining in O(1)?
Create a calculator class with a variable storing the current result. Each method updates that variable using the requested arithmetic operation and returns the same instance (self or this). Because every operation is a constant-time arithmetic update, the complexity remains O(1) per call.
What is the best approach for Calculator with Method Chaining?
The standard solution uses a class that stores the current value and returns the same instance from every arithmetic method. Each method performs the operation, updates the internal state, and returns self or this so calls can be chained. This design runs in O(1) time per operation and O(1) space.
Is Calculator with Method Chaining asked at Google/Amazon/Meta?
Method chaining and fluent interface design appear in object-oriented design interviews at companies like Amazon, Google, and Meta. The exact problem may vary, but the concept of returning the current object to enable chained API calls is a common design pattern interviewers expect candidates to understand.
What data structure is used in Calculator with Method Chaining?
The solution primarily relies on object-oriented class design rather than a traditional data structure. The class maintains a single numeric state variable and exposes methods that modify it while returning the instance to support chaining.
What is the time complexity of Calculator with Method Chaining?
Each calculator operation such as add, subtract, multiply, or divide performs a single arithmetic update on the stored value. That makes the time complexity O(1) per method call and the space complexity O(1) because only one numeric value is stored.

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