To Be Or Not To Be - Practice Coding Problems

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

Tap to expand

Understanding the Visualization

Input

expect(5) receives value to test against

Process

Returns object with toBe/notToBe assertion methods

Usage

Methods compare values and return true or throw errors

Key Takeaway

🎯 Key Insight: Use closures to preserve the original value and return methods that can perform assertions against it

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

Approach	Time	Space	Notes
✓ Factory Function Pattern	O(1)	O(1)	Use factory function pattern with method binding for cleaner implementation
Direct Object Return	O(1)	O(1)	Return an object literal with comparison methods using direct value capture

Factory Function Pattern — Algorithm Steps

Create expect factory function
Define assertion methods with proper context binding
Use arrow functions to maintain lexical scope
Implement error handling with descriptive messages

Visualization

Tap to expand

Step-by-Step Walkthrough

Factory Function

expect() acts as a factory

Object Creation

Creates assertion object with methods

Method Binding

Methods bound to original value via closure

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) {
        fprintf(stderr, "Not Equal\n");
        exit(1);
    }
    
    if (obj->type == 0) {
        if (*(int*)obj->val == *(int*)expected) {
            return true;
        }
    } else {
        if (strcmp((char*)obj->val, (char*)expected) == 0) {
            return true;
        }
    }
    
    fprintf(stderr, "Not Equal\n");
    exit(1);
}

bool notToBe(ExpectObject* obj, void* expected, int expectedType) {
    if (obj->type != expectedType) {
        return true;
    }
    
    if (obj->type == 0) {
        if (*(int*)obj->val != *(int*)expected) {
            return true;
        }
    } else {
        if (strcmp((char*)obj->val, (char*)expected) != 0) {
            return true;
        }
    }
    
    fprintf(stderr, "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)

All operations are constant time comparisons

✓ Linear Growth

Space Complexity

O(1)

Only creates function objects and maintains value references

✓ Linear Space

28.5K Views

Medium Frequency

~8 min Avg. Time

892 Likes

Ln 1, Col 1

Smart Actions

💡 Explanation

AI Ready

💡 Suggestion Tab to accept Esc to dismiss

// Output will appear here after running code

Code Editor Closed

Click the red button to reopen

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Factory Function Pattern — Algorithm Steps

Visualization

Code -

Time & Space Complexity

Select Compiler