Thread: Need some help on c++ assignment

I already completed one part of the assignment, but need help on the other part. The assignment was to create two recursive functions. One that converts strings to integers ( which i completed) and the other converts integers to strings.

I need help on the last function.

This is the prototype: string intToStr(int n);

What have you tried? Can you use the ostringstream class?

Jim

If you are not allowed to use ostringstream class,which probably don't,you may have to take a look at itoa itoa - C++ Reference

We are not allowed to use any functions that are similar to atoi or itoa. We also cannot use for or while.

This is my other function that converts the string to an integer:

Code:

int stringToInt(string str)
{
    static bool OK; //This variable signals if the string can be treated as int
    static int sign; //This variable signals about the sign of the number
   
   
    OK = true;
    sign = 0;

    int digit = 0; // The result of the function

    int length = str.length();

  
    if (length == 2) {
        if (str[0] == '-')
            sign = -1;
        else if (str[0] == '+')
            sign = +1;
    }

   
    if (length == 1 || length == 2 && sign != 0) {
       
        if (str[length-1] < '0' || str[length-1] > '9') {
            
            OK = false;
            return 0;
        }
      
        digit = str[length-1] - '0';
        
        if (sign == -1) digit = -digit;
    }
    // The main case:
    else {
       
        digit = stringToInt(str.substr(0, length-1));
      
        if (!OK) return 0;
        
        digit *= 10;
       
        if (str[length-1] < '0' || str[length-1] > '9') {
            OK = false;
            return 0;
        }
       
        if (sign == -1) // If the sign is minus, then do it by subtracting
            digit -= str[length-1] - '0';
        else // otherwise, do it by adding
            digit += str[length-1] - '0';
    }
    // Return the final result
    return digit;
}

Originally Posted by iMalc

That seems a bit large, so probably a lot that can be improved upon there. Are you sure that you're allowed to use static variables?

You still haven't posted your attempt at intToStr though, or asked any questions about it, so we can't help you with that yet. The good news is that it's easier than the other way around.

Not sure about static variables. As for intToStr. I haven't started it yet. I would like some help with the base case of the recursive part.

Originally Posted by iMalc

The base case would be that the input is from 0 to 9, and all you need to do is return that digit as a string.
Yes the base case really is that simple!

That clearly leaves negative values, and values of 10 or greater, as remaining cases. Now code that up and have a go at the remaining cases then post your attempt.

So it would be like this? if(n==0) return 0?

How would you return it as a string? Also could you also provide some advice on the main function? Would I be using the same main function as I did for stringToInt? Thank-you!

Here is what I have so far:

Code:

#include <iostream>#include <string>


using namespace std;


//recursive function prototype
string intToStr(int n);


//main
int main()
{


	/*/int tests[] = {
		0, 100, -5, 10, 5, 10302
	};


	const int B = 6;
	for (int i=0; i<B; i++)
	{
		cout << "Converting the integer "<< tests[i] <<" to string: ";
		cout << intToStr(tests[i]) << endl;
	}*/




	int num;


	cout<<"Please input a number: ";
	cin>>num;
	cout<<endl;


	cout<<"Converting the integer "<<num<<" to a string: ";
	cout<<intToStr(num)<<endl;


	//string str;


	system("PUASE");
	return 0;
}


string intToStr(int n)
{
	if (










}

I need help with setting up the base case. I think it looks like this for int 0?

if(?==0) return 0;

How do you convert that to a string and return it?

How would the remaining cases look like? I sorta remember my instuctor talking about using either division or modulo(%)?