Question

Many programming languages have some kind list data structure, which allows for insertion and deletion of elements, essentially an array that changes size. C++ has vectors, Java has the ArrayList, Python has lists (which is what they're called generically anyway). But how do they really work? All of these actually use arrays, which naturally have immutable lengths.

Your task is to write a function, insert, which inserts a new item into an existing array, then returns the modified array. Since you can not really do this, you will have create a new array which has all the elements of the original array, plus the new item in its proper place, and return that new array instead. This is how lists actually work. I won't make you write the code for deleting items; after you do this, you'll understand how it works anyway.

You may notice that the return type of insert is a pointer to an integer. This is fine, since an array is just a pointer to the first item in the array.

2 points for each:

• Adds the new item to the array

• Inserts the new item in the correct place

• Does not remove any items from the array

• Does not cause any memory leaks, segmentation faults, etc

• Comments explains how it works

  
  

  
  

  
  

  The starter code is listed bellow

  #include <iostream> /* * insert takes an array of ints and inserts an item * at a given index, shifting all elements to the right * to make room for it as needed. There must be a * length number of integers in the array. It then * returns the new array with item inserted correctly. * * If index >= length, item is appended to the array * If index < 0, insertion point is calculated counting * from the end of the array. -1 = length-1, etc. */ int * insert(int arr[], int length, int item, int index); /* * print takes an array of ints and prints it * with spaces between each item. There must be * a length number of integers. */ void print(int arr[], int length); int main() { //These next two lines make an array and put numbers in it int * numbers = new (std::nothrow) int [4]; for(int i = 0; i < 4; i++) { numbers[i] = (i * 2) + 2; } //Prints 2 4 6 8 print(numbers, 4); numbers = insert(numbers, 4, 100, 2); //Prints 2 4 100 6 8 print(numbers, 5); //Feel free to add your own test cases here, // to make sure your function works //Memory cleanup delete [] numbers; return 0; } int * insert(int arr[], int length, int item, int index) { //YOUR CODE GOES HERE return arr; //Delete this line } void print(int arr[], int length) { for(int i = 0; i < length; i++) { std::cout << arr[i] << " "; } std::cout << std::endl; }

Answer 1

Program:

#include <iostream>
/* * insert takes an array of ints and inserts an item
* at a given index, shifting all elements to the right
* to make room for it as needed. There must be a
* length number of integers in the array. It then
* returns the new array with item inserted correctly.
* If index >= length, item is appended to the array
* If index < 0, insertion point is calculated counting
* from the end of the array. -1 = length-1, etc. */

int * insert(int arr[], int length, int item, int index);

/* * print takes an array of ints and prints it
* with spaces between each item. There must be
* a length number of integers. */

void print(int arr[], int length);

int main()
{
//These next two lines make an array and put numbers in it
int * numbers = new (std::nothrow) int [4];

for(int i = 0; i < 4; i++)
{
numbers[i] = (i * 2) + 2;
}

//Prints 2 4 6 8
print(numbers, 4);
numbers = insert(numbers, 4, 100, 2);
//Prints 2 4 100 6 8
print(numbers, 5);
//Feel free to add your own test cases here,
// to make sure your function works
//Memory cleanup
delete [] numbers;

return 0;
}

int * insert(int arr[], int length, int item, int index)
{
//create a new array
int *numbers = new (std::nothrow) int [length + 1];

//copy all the elements of the original array
for(int i = 0; i < length; i++)
{
numbers[i] = arr[i];
}

if(index < 0) index = length + index;

//shifting all elements to the right
for(int i=length; i>=index; i--)
{
numbers[i] = numbers[i-1];
}

//insert new item in its proper place
numbers[index] = item;

//Memory cleanup
delete [] arr;

//return the new array
return numbers;
}

void print(int arr[], int length)
{
for(int i = 0; i < length; i++)
{
std::cout << arr[i] << " ";
}

std::cout << std::endl;
}

Output:

N.B. Whether you face any problem then share with me in the comment section, I'll happy to help you.