Question

In C++ please. Thank you!!

#include <iostream>
#include <cstring>

// print an array backwards, where 'first' is the first index
// of the array, and 'last' is the last index 
void writeArrayBackward(const char anArray[], int first, int last) {
  int i = 0;

  for (i = last; i >= first; i--) {
    std::cout << anArray[i];
  }
  std::cout << std::endl;
}

// test driver
int main() {
  const char *s = "abc123";
  writeArrayBackward(s, 0, strlen(s) - 1);
}

// Using the above iterative version of writeArrayBackward as a reference, write a recursive version of this function, but with a couple of twists:

1) Your function will only write the Nth character of the array, supplied as a parameter by the caller. This is an example prototype (although you may want to change the return value type, based on the second twist, below).

void writeArrayNthBackward(const char [], int, int, int);

The first three arguments serve the same purpose as in the iterative example. The fourth argument (an int) supplies the N for the Nth character to print in the array. If n == 1, then the string is printed normally in reverse (no characters are dropped). If n == 2, then every "other" character is printed, and so on.

You can constrain N to be 1 <= N <= 3.

Your code does NOT need to output a newline ('endl') within the recursive function itself (as the above iterative version does), you can output the newline after the return of the function.

2) If any of the removed characters in the string were numbers (not letters), output their sum. For example, if your function removed the numbers 3 and 1 from the string 'abc123', the result would be 3 plus 1, which is 4. See the below table for more examples..

Converting a String Digit to an Integer

If you have a string and want to convert a character in the string to an int, there are a few ways to do it. The easiest is probably this one:

char *a = "123";
int n;
n = (int)a[0] - '0';

Notice we can't simply cast a[0] to an int, because that will give us the ASCII code for the character '1', which is 49. We want the value of 'n' to be 1, so by subtracting the ASCII code for 0 (which is 48), it "translates" the character to an integer value.

What to Submit in Canvas

Submit both a test driver main() function (that tests at least all the below examples) as well as your writeArrayNthBackward function. You can submit the entire lab in a single file if you prefer (the function and a driver main()) together in one .cpp file.

Example inputs and outputs:

Input string	N	Output
abc123	2	2ca (sum of numbers removed: 4)
hello	1	olleh (sum of numbers removed: 0)
hello	3	l (sum of numbers removed: 0)
c1c1c1	2	ccc (sum of numbers removed: 3)

Answer 1

C++ code in dev-c++ :-

#include <iostream>
#include <cstring>
using namespace std;

// print an array backwards, where 'first' is the first index
// of the array, and 'last' is the last index
void writeArrayBackward(const char anArray[], int first, int last, int n) {
int m=0,count=0,x=0,j=0;
if(n==1){

int i = 0;

for (i = last; i >= first; i--) {
std::cout << anArray[i];
}
std::cout << std::endl;
}
else if(n>=2)
{
   j=n-1;
for (int i = last; i > n; i--) {
   x=i-j;
   //cout<<x<<endl;
   m = (int)anArray[x+1] - '0';
   //cout<<m<<endl;
   if( m> 0 && m <= 9 ) count+=m;
   //cout<<count<<endl;
std::cout << anArray[x] ;
j=j+n-1;
}
cout<<"(sum of numbers removed: "<<count<<")"<<endl;
}
}

// test driver
int main() {
const char *s = "c1c1c1";
int choice;
cout << "enter the choice:" <<endl;
cin>>choice;
  
writeArrayBackward(s, 0, strlen(s) - 1,choice);
}

Output:-

changing the string to hello and then the output will be:-

changing the string to c1c1c1 and then the output will be:-

If you didn't understood the code or need any further clarification or modification please do comment.

Thank you