Array Wrapper - Practice Coding Problems

Array Wrapper - Problem

JavaScript Easy

Create a class ArrayWrapper that accepts an array of integers in its constructor. This class should have two features:

Addition Operator: When two instances of this class are added together with the + operator, the resulting value is the sum of all the elements in both arrays.

String Conversion: When the String() function is called on the instance, it will return a comma separated string surrounded by brackets. For example, [1,2,3].

Input & Output

Example 1 — Basic Addition and String

$ Input: nums1 = [1,2], nums2 = [3,4]

› Output: [10, "[1,2]"]

💡 Note: obj1 + obj2 = (1+2) + (3+4) = 3 + 7 = 10. String(obj1) = "[1,2]"

Example 2 — Empty Array

$ Input: nums1 = [], nums2 = [5]

› Output: [5, "[]"]

💡 Note: obj1 + obj2 = 0 + 5 = 5. String(obj1) = "[]" for empty array

Example 3 — Negative Numbers

$ Input: nums1 = [-1,-2], nums2 = [1]

› Output: [-2, "[-1,-2]"]

💡 Note: obj1 + obj2 = (-1+-2) + 1 = -3 + 1 = -2. String includes negative numbers

Constraints

1 ≤ nums.length ≤ 1000
-1000 ≤ nums[i] ≤ 1000

Visualization

Tap to expand

Understanding the Visualization

Input

Two arrays [1,2] and [3,4] wrapped in ArrayWrapper objects

Process

Addition operator sums all elements, String() formats with brackets

Output

Returns [10, "[1,2]"] - sum and string representation

Key Takeaway

🎯 Key Insight: JavaScript's valueOf() and toString() methods enable seamless operator overloading

Asked in

G Google 15 f Facebook 12 M Microsoft 8

Create a class with valueOf() for addition operator overloading and toString() for string conversion. The key insight is using JavaScript's built-in operator overloading through these special methods. Best approach uses reduce() and join() for clean implementation. Time: O(n), Space: O(1)

Common Approaches

Approach	Time	Space	Notes
✓ Built-in Array Methods	O(n)	O(1)	Use JavaScript's built-in array methods for cleaner implementation
Manual Implementation	O(n)	O(1)	Implement addition and string conversion with basic loops

Built-in Array Methods — Algorithm Steps

Create ArrayWrapper class
Use reduce() in valueOf() for sum
Use join() in toString() for formatting

Visualization

Tap to expand

Step-by-Step Walkthrough

Create Objects

Initialize ArrayWrapper instances

reduce() Sum

Use reduce to calculate sum efficiently

join() Format

Use join for clean string formatting

Code -

solution.c — C

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

typedef struct {
    int* nums;
    int size;
} ArrayWrapper;

int valueOf(ArrayWrapper* aw) {
    int sum = 0;
    for (int i = 0; i < aw->size; i++) {
        sum += aw->nums[i];
    }
    return sum;
}

char* toString(ArrayWrapper* aw) {
    char* result = malloc(1000);
    strcpy(result, "[");
    for (int i = 0; i < aw->size; i++) {
        if (i > 0) strcat(result, ",");
        char num_str[20];
        sprintf(num_str, "%d", aw->nums[i]);
        strcat(result, num_str);
    }
    strcat(result, "]");
    return result;
}

char** solution(int* nums1, int size1, int* nums2, int size2) {
    ArrayWrapper obj1 = {nums1, size1};
    ArrayWrapper obj2 = {nums2, size2};
    int sum = valueOf(&obj1) + valueOf(&obj2);
    char* str = toString(&obj1);
    
    char** result = malloc(2 * sizeof(char*));
    result[0] = malloc(20);
    result[1] = malloc(strlen(str) + 1);
    sprintf(result[0], "%d", sum);
    strcpy(result[1], str);
    free(str);
    return result;
}

int main() {
    int nums1[] = {1, 2};
    int nums2[] = {3, 4};
    char** result = solution(nums1, 2, nums2, 2);
    printf("[\"%s\",\"%s\"]\n", result[0], result[1]);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n)

Array.reduce() and Array.join() each iterate once through the array

✓ Linear Growth

Space Complexity

O(1)

Only stores reference to input array, built-in methods handle intermediate operations

✓ Linear Space

12.0K Views

Medium Frequency

~15 min Avg. Time

450 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

Built-in Array Methods — Algorithm Steps

Visualization

Code -

Time & Space Complexity

Select Compiler