number in a string

[mimis]

Hi,
I am trying to write a program that will read an integer as a string and it will add 1 to this integer. For example if it read 234, it will return 235.

My attempt is this:

#include <fstream>
#include <string>
using namespace std;

void addone(string& num){
	int n=num.size();
	int i=n-1;
	
	while(num[i]=='9'){
		if (i==0){
			num[i]=1;
			for (int j=1;j<=n;j++){
				num[j]='0';
			}
		}
		
		num[i]='0';
		i--;
	}
	if (i>=0){
		num[i]=num[i]+1;
	}
}
		

int main()
{
	ifstream in("something.in");
	ofstream out("something.out");
	
	string num;
	in >> num;
	
	addone(num);
	
	out << num;
	
	return 0;
}

This code works good generally.
The only problem is that if the number has only 9s it outputs only 0s without 1.

Can you help me to fix this problem?

[tesuji]

hi mimis

num[i]=1;

// maybe if you replace this by

num[i]=0x31; //ascii coding for numeric 1 is hex 31 (third column, first row) or simpler num[i]='1';
 
// it will work

(didn't check rest of your code)

-- tesu

Whaats all this crazy bs?

Convert the string to an int using stringstreams then add one to it.

[tesuji]

Well, there might also be some ordinary mortals who GOT to do there profane programming homework when studying first-year computer sciences.

[Ancient Dragon]

>>do there profane programming

Its their not there. :) And yes, we were all beginners at one time or another.

[tesuji]

Thank you Dragon, I am still absolute beginner at English :(

-- tesu

[mimis]

Thank you for your answers.

My second attemp was that:

#include <fstream>
#include <cstring>
#include <stdlib.h>
#include <string>
using namespace std;

int main()
{
	ifstream in("something.in");
	ofstream out("something.out");
	
	string num;
	stringstream ss;
	in >> num;
	
	int i,temp;
	
	temp= atoi(num.c_str()); 
	temp++;
	ss << temp;
	num=ss.str();
	
	
	out <<num;
	
	return 0;
}

But the compiler appear that error:
runaround.cpp:12: error: aggregate ‘std::stringstream ss’ has incomplete type and cannot be defined

I tried to do it with itoa but the compiler appear that itoa is not declered in this scope.

[Ancient Dragon]

I have to include <sstream> header file. And you don't need atoi() because stringstream is a safer way to convert the string to an int.

[Software guy]

Hi,
I looked at the task and found it interesting... So i did the code, you can get the algorithm for "9". Hope this helps

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

int main()
{
	while(1){
	char c[2];
	int i=0, factor=0,max=0;
         int sub;
	string  a; 

	cout<<"\nEnter the integer:";
	cin>>a;
    
	sub= a.size();

	c[1] = a[sub-1];
         c[0] = a[0];
	max = a.size();
	cout<<"Last Integer Found:"<<c[1]<<"\n";
       

	if (c[0]=='9' && c[1] =='9')//if the first and last element is 9
	{
	     cout<<"\n1";

		 for(i=0;i<=a.size()-1;i++)
		 {
			 cout<<"0";
	          }
	}
	
       else if(c[1]== '9')//if the last element is 9
       {
	  
                 for(i=a.size()-1;i>-1;i--)
	     {
                    if(a[i] == c[1])
	    	{
			
			factor=i;
			
		       if(factor<max)
			      {max = factor;}



		 }
	   
		else if(a[i]!=c[1])
		{/*Do Nothing*/}

		 
	     }
	  
	   cout<<"\nLargest 9 found was element:"<<max<<"\n";

	   cout<<"Calculating using Finding NINE Method.....";

	   a[max-1] = (int)a[max-1] + 1;

	   i = 0;
  
	   for(i=max;i<=a.size();i++)
	   {
		   a[i]= '0';
	   }



	   cout<<"\nNew value is :"<<a<<"\n";
}

	else if(c[1]!='9')//if the last element is not 9
	{
		cout<<"9 Not detected Performing Normal Procedure\n";
	
		sub  = 0;

	    sub = (int)c[1];

	    sub = sub + 1;
       
        a[a.size()-1] = (char) sub; 
      
		cout<<"The new Integer is:"<<a<<"\n";

	}
   
}
	return 0;

}

Compiled it using VC++ 2008 and works perfectly.

itoa doesn't even exist in the standard.

Use this for reference.
http://faq.cprogramming.com/cgi-bin/smartfaq.cgi?answer=1046996179&id=1043284385

#include <iostream>
#include <string>
#include <sstream>

int main()
{
   //convert string to int then add one
   std::string s = "234";
   std::istringstream myStream ( s );

   int i;
   myStream >> i;

   std::cout << i + 1;

   std::cin.get();
}