Array Wrapper

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

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

Manual Implementation — Algorithm Steps

Create ArrayWrapper class with constructor
Implement valueOf() to sum all elements
Implement toString() to format as bracketed string

Visualization

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Step-by-Step Walkthrough

Create Wrappers

Wrap arrays in ArrayWrapper objects

Manual Sum

Loop through each array to calculate sums

String Format

Build bracketed string with comma separation

Code -

solution.c — C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.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;
}

int* parseArray(char* line, int* size) {
    *size = 0;
    int* nums = malloc(1000 * sizeof(int));
    char* token = strtok(line, "[],");
    
    while (token != NULL) {
        while (*token == ' ') token++;
        if (*token != '\0') {
            nums[(*size)++] = atoi(token);
        }
        token = strtok(NULL, "[],");
    }
    return nums;
}

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() {
    char line1[1000], line2[1000];
    fgets(line1, sizeof(line1), stdin);
    fgets(line2, sizeof(line2), stdin);
    
    int size1, size2;
    int* nums1 = parseArray(line1, &size1);
    int* nums2 = parseArray(line2, &size2);
    
    char** result = solution(nums1, size1, nums2, size2);
    printf("[\"%s\",\"%s\"]\n", result[0], result[1]);
    
    free(nums1);
    free(nums2);
    free(result[0]);
    free(result[1]);
    free(result);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n)

Must iterate through array once for sum or string conversion

✓ Linear Growth

Space Complexity

O(1)

Only stores reference to input array, no extra space

✓ Linear Space

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Input & Output

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Common Approaches

Manual Implementation — Algorithm Steps

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Code -

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