LeetCode #2726 — EASY

Calculator with Method Chaining

Build confidence with an intuition-first walkthrough focused on core interview patterns fundamentals.

The Problem

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"

Step 01

Brute Force Baseline

Problem summary: 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

Baseline thinking

Start with the most direct exhaustive search. That gives a correctness anchor before optimizing.

Pattern signal: General problem-solving

Example 1

["Calculator", "add", "subtract", "getResult"]
[10, 5, 7]

Example 2

["Calculator", "multiply", "power", "getResult"]
[2, 5, 2]

Example 3

["Calculator", "divide", "getResult"]
[20, 0]

Step 02

Core Insight

What unlocks the optimal approach

No official hints in dataset. Start from constraints and look for a monotonic or reusable state.

Interview move: turn each hint into an invariant you can check after every iteration/recursion step.

Step 03

Algorithm Walkthrough

Iteration Checklist

Define state (indices, window, stack, map, DP cell, or recursion frame).
Apply one transition step and update the invariant.
Record answer candidate when condition is met.
Continue until all input is consumed.

Use the first example testcase as your mental trace to verify each transition.

Step 04

Edge Cases

Minimum Input

Single element / shortest valid input

Validate boundary behavior before entering the main loop or recursion.

Duplicates & Repeats

Repeated values / repeated states

Decide whether duplicates should be merged, skipped, or counted explicitly.

Extreme Constraints

Upper-end input sizes

Re-check complexity target against constraints to avoid time-limit issues.

Invalid / Corner Shape

Empty collections, zeros, or disconnected structures

Handle special-case structure before the core algorithm path.

Step 05

Full Annotated Code

Source-backed implementations are provided below for direct study and interview prep.

// Accepted solution for LeetCode #2726: Calculator with Method Chaining
// Auto-generated Java example from ts.
class Solution {
    public void exampleSolution() {
    }
}
// Reference (ts):
// // Accepted solution for LeetCode #2726: Calculator with Method Chaining
// class Calculator {
//     private x: number;
// 
//     constructor(value: number) {
//         this.x = value;
//     }
// 
//     add(value: number): Calculator {
//         this.x += value;
//         return this;
//     }
// 
//     subtract(value: number): Calculator {
//         this.x -= value;
//         return this;
//     }
// 
//     multiply(value: number): Calculator {
//         this.x *= value;
//         return this;
//     }
// 
//     divide(value: number): Calculator {
//         if (value === 0) {
//             throw new Error('Division by zero is not allowed');
//         }
//         this.x /= value;
//         return this;
//     }
// 
//     power(value: number): Calculator {
//         this.x **= value;
//         return this;
//     }
// 
//     getResult(): number {
//         return this.x;
//     }
// }

// Accepted solution for LeetCode #2726: Calculator with Method Chaining
// Auto-generated Go example from ts.
func exampleSolution() {
}
// Reference (ts):
// // Accepted solution for LeetCode #2726: Calculator with Method Chaining
// class Calculator {
//     private x: number;
// 
//     constructor(value: number) {
//         this.x = value;
//     }
// 
//     add(value: number): Calculator {
//         this.x += value;
//         return this;
//     }
// 
//     subtract(value: number): Calculator {
//         this.x -= value;
//         return this;
//     }
// 
//     multiply(value: number): Calculator {
//         this.x *= value;
//         return this;
//     }
// 
//     divide(value: number): Calculator {
//         if (value === 0) {
//             throw new Error('Division by zero is not allowed');
//         }
//         this.x /= value;
//         return this;
//     }
// 
//     power(value: number): Calculator {
//         this.x **= value;
//         return this;
//     }
// 
//     getResult(): number {
//         return this.x;
//     }
// }

# Accepted solution for LeetCode #2726: Calculator with Method Chaining
# Auto-generated Python example from ts.
def example_solution() -> None:
    return
# Reference (ts):
# // Accepted solution for LeetCode #2726: Calculator with Method Chaining
# class Calculator {
#     private x: number;
# 
#     constructor(value: number) {
#         this.x = value;
#     }
# 
#     add(value: number): Calculator {
#         this.x += value;
#         return this;
#     }
# 
#     subtract(value: number): Calculator {
#         this.x -= value;
#         return this;
#     }
# 
#     multiply(value: number): Calculator {
#         this.x *= value;
#         return this;
#     }
# 
#     divide(value: number): Calculator {
#         if (value === 0) {
#             throw new Error('Division by zero is not allowed');
#         }
#         this.x /= value;
#         return this;
#     }
# 
#     power(value: number): Calculator {
#         this.x **= value;
#         return this;
#     }
# 
#     getResult(): number {
#         return this.x;
#     }
# }

// Accepted solution for LeetCode #2726: Calculator with Method Chaining
// Rust example auto-generated from ts reference.
// Replace the signature and local types with the exact LeetCode harness for this problem.
impl Solution {
    pub fn rust_example() {
        // Port the logic from the reference block below.
    }
}

// Reference (ts):
// // Accepted solution for LeetCode #2726: Calculator with Method Chaining
// class Calculator {
//     private x: number;
// 
//     constructor(value: number) {
//         this.x = value;
//     }
// 
//     add(value: number): Calculator {
//         this.x += value;
//         return this;
//     }
// 
//     subtract(value: number): Calculator {
//         this.x -= value;
//         return this;
//     }
// 
//     multiply(value: number): Calculator {
//         this.x *= value;
//         return this;
//     }
// 
//     divide(value: number): Calculator {
//         if (value === 0) {
//             throw new Error('Division by zero is not allowed');
//         }
//         this.x /= value;
//         return this;
//     }
// 
//     power(value: number): Calculator {
//         this.x **= value;
//         return this;
//     }
// 
//     getResult(): number {
//         return this.x;
//     }
// }

// Accepted solution for LeetCode #2726: Calculator with Method Chaining
class Calculator {
    private x: number;

    constructor(value: number) {
        this.x = value;
    }

    add(value: number): Calculator {
        this.x += value;
        return this;
    }

    subtract(value: number): Calculator {
        this.x -= value;
        return this;
    }

    multiply(value: number): Calculator {
        this.x *= value;
        return this;
    }

    divide(value: number): Calculator {
        if (value === 0) {
            throw new Error('Division by zero is not allowed');
        }
        this.x /= value;
        return this;
    }

    power(value: number): Calculator {
        this.x **= value;
        return this;
    }

    getResult(): number {
        return this.x;
    }
}

Step 06

Interactive Study Demo

Use this to step through a reusable interview workflow for this problem.

Custom checkpoints (one per line)

Press Step or Run All to begin.

Step 07

Complexity Analysis

Time

O(n)

Space

O(1)

Approach Breakdown

BRUTE FORCE

O(n²) time

O(1) space

Two nested loops check every pair or subarray. The outer loop fixes a starting point, the inner loop extends or searches. For n elements this gives up to n²/2 operations. No extra space, but the quadratic time is prohibitive for large inputs.

OPTIMIZED

O(n) time

O(1) space

Most array problems have an O(n²) brute force (nested loops) and an O(n) optimal (single pass with clever state tracking). The key is identifying what information to maintain as you scan: a running max, a prefix sum, a hash map of seen values, or two pointers.

Shortcut: If you are using nested loops on an array, there is almost always an O(n) solution. Look for the right auxiliary state.

Coach Notes

Common Mistakes

Review these before coding to avoid predictable interview regressions.

Off-by-one on range boundaries

Wrong move: Loop endpoints miss first/last candidate.

Usually fails on: Fails on minimal arrays and exact-boundary answers.

Fix: Re-derive loops from inclusive/exclusive ranges before coding.