Question

I was trying the Open Courseware CS106b assignment 1. I am getting stuck on problem 4 which requires the use of recursion to write an integer to string convertor. We are not allowed to use any library functions that perform integer conversions.

The problem is that after every ‘recursion level’ the code does not keep track of the previous string, thus I am not able to append and build-onto the string.

 #include <iostream>
 #include <string>
 #include "console.h"
 #include "simpio.h"
 using namespace std;

/* Function prototypes */

string intToString(int n);
int stringToInt(string str);

/* Main program */

int main() {
    // [TODO: fill in the code]
    int n = getInteger("Enter number for conversion to String: ");
    cout<< "Converted to String: "<<intToString(n);
    return 0;
}

//Functions

string intToString(int n){
    double toBeDecomposed = n;
    string convertedToString;
    char ch;
    string tempString;

    if((double)(toBeDecomposed/10) >= 0.1){

        int lastDigit = (int)toBeDecomposed%10;

        toBeDecomposed = (int)(toBeDecomposed/10);

        intToString(toBeDecomposed);

        if (lastDigit == 0) {
            ch = '0';
        }
        else if (lastDigit == 1) {
            ch = '1';
        }
        else if (lastDigit == 2) {
            ch = '2';
        }
        else if (lastDigit == 3) {
            ch = '3';
        }
        else if (lastDigit == 4) {
            ch = '4';
        }
        else if (lastDigit == 5) {
            ch = '5';
        }
        else if (lastDigit == 6) {
            ch = '6';
        }
        else if (lastDigit == 7) {
            ch = '7';
        }
        else if (lastDigit == 8) {
            ch = '8';
        }
        else if (lastDigit == 9) {
            ch = '9';
        }

        tempString = string() + ch;

        convertedToString = convertedToString.append(tempString);

        cout<<convertedToString<<endl;

    }
    cout<<"Returning: "<<convertedToString<<endl;

    return convertedToString;
}

int stringToInt(string str){
    return 0; 
}

My debugging output shows that it only returns the last digit:

Can anyone suggest how to successfully append to the string ConvertedToString so that I return the whole converted integer?

Answer 1

You aren’t doing anything with the result of your recursive function call.

The hint is that intToString returns a string. You’re ignoring that return value when you call intToString(toBeDecomposed);.

Capture that return value and do something with it.