To Be Or Not To Be

To Be Or Not To Be - Problem

JavaScript Easy

Write a function expect that helps developers test their code. It should take in any value val and return an object with the following two functions:

toBe(val) accepts another value and returns true if the two values === each other. If they are not equal, it should throw an error "Not Equal".
notToBe(val) accepts another value and returns true if the two values !== each other. If they are equal, it should throw an error "Equal".

This is similar to Jest or Chai assertion libraries used in JavaScript testing frameworks.

Input & Output

Example 1 — toBe Success

$ Input: expect(5).toBe(5)

› Output: true

💡 Note: Since 5 === 5, the toBe method returns true without throwing an error

Example 2 — toBe Failure

$ Input: expect(5).toBe(null)

› Output: throws "Not Equal"

💡 Note: Since 5 !== null, the toBe method throws an error with message "Not Equal"

Example 3 — notToBe Success

$ Input: expect(5).notToBe(null)

› Output: true

💡 Note: Since 5 !== null, the notToBe method returns true without throwing an error

Constraints

val can be any JavaScript value (primitive or object)
toBe and notToBe methods should use strict equality (=== and !==)
Error messages must be exactly "Not Equal" and "Equal"

Visualization

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Asked in

M Meta 35 G Google 28 M Microsoft 22 A Amazon 18

The key insight is to use closures to capture the original value and return an object with comparison methods. The optimal approach returns an object with toBe and notToBe methods that use strict equality. Time: O(1), Space: O(1)

Common Approaches

✓ Direct Object Return

⏱️ Time: O(1) Space: O(1)

Create a function that returns an object with toBe and notToBe methods. Each method directly compares values using strict equality and throws errors when conditions aren't met.

Factory Function Pattern

⏱️ Time: O(1) Space: O(1)

Implement expect as a factory function that creates assertion objects. This approach uses JavaScript's function binding and prototype patterns for a more structured solution.

Direct Object Return — Algorithm Steps

Create expect function that takes a value
Return object with toBe and notToBe methods
Use strict equality (===) and inequality (!==) for comparisons
Throw descriptive errors when assertions fail

Visualization

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Step-by-Step Walkthrough

Input Value

Store the expected value in closure

Return Object

Create object with toBe and notToBe methods

Method Calls

Methods compare and return true or throw errors

Code -

solution.c — C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>

typedef struct {
    void* val;
    int type; // 0 for int, 1 for string
} ExpectObject;

bool toBe(ExpectObject* obj, void* expected, int expectedType) {
    if (obj->type != expectedType) {
        printf("Not Equal\n");
        exit(1);
    }
    
    if (obj->type == 0) { // int
        if (*(int*)obj->val == *(int*)expected) {
            return true;
        }
    } else { // string
        if (strcmp((char*)obj->val, (char*)expected) == 0) {
            return true;
        }
    }
    
    printf("Not Equal\n");
    exit(1);
}

bool notToBe(ExpectObject* obj, void* expected, int expectedType) {
    if (obj->type != expectedType) {
        return true;
    }
    
    if (obj->type == 0) { // int
        if (*(int*)obj->val != *(int*)expected) {
            return true;
        }
    } else { // string
        if (strcmp((char*)obj->val, (char*)expected) != 0) {
            return true;
        }
    }
    
    printf("Equal\n");
    exit(1);
}

ExpectObject solution(void* val, int type) {
    ExpectObject obj;
    obj.val = val;
    obj.type = type;
    return obj;
}

int main() {
    char input[1000];
    fgets(input, sizeof(input), stdin);
    input[strcspn(input, "\n")] = 0;
    
    ExpectObject result = solution(input, 1);
    printf("function\n");
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

Each comparison operation is constant time

✓ Linear Growth

Space Complexity

O(1)

Only stores references to values and function objects

✓ Linear Space

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Medium Frequency

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Smart Actions

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Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Direct Object Return — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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