how do i create a function that adds the contents of 2 strings of numbers, only n8umbers that does not use + or - or atoi function or of the like
add_strings("123", "66")
would return "189"
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how do i create a function that adds the contents of 2 strings of numbers, only n8umbers that does not use + or - or atoi function or of the like
add_strings("123", "66")
would return "189"
your saying you cant use a standard library function that would convert a string to an int? if so then your question is basically 'how do i write atoi?'. if this is the case, then try it out on paper how you would do it (ie without 'programming' or using a computer), and post your attempts or thoughts.
make a db of pre determined additions of x and y add[10][10] = ('0', '1', '2' etc)
and than another db of carries
what? if you want help please be more elaborate :)
first, answer the question from my first post: you have to do this without functions such as 'atoi' right? and your edit didnt make it much more clear or elaborate! please dont use shortforms and explain what you are saying.
It seems like you already know the answer, and just looking for someone else to do the work.
it sound exctly like my hw..
but here is the answer.
Code:/***************************************************************************
* How to add two postive numbers?
*
* Sun Apr 22 09:25:07 2007
* Jabka Atu
*
****************************************************************************/
/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include <iostream>
using namespace std;
char* add_two_postive_numbers(char *first_value,char *second_value){
char *result=NULL;
char i=0;
char ans='0';
char carry=0;
char size_of_first = strlen(first_value);
char size_of_second = strlen(second_value);
char biggest_size = (size_of_first > size_of_second) ? size_of_first : size_of_second;
char smallest_size = (size_of_first < size_of_second) ? size_of_first : size_of_second;
char delta = size_of_first - size_of_second;
if (size_of_first < size_of_second)
{
result=add_two_postive_numbers(second_value,first_value);
return result;
}
result=new char[biggest_size + 2];//one more for '\0' and for extra 1
result[biggest_size + 1] = '\0';
result[0] = '0';
for (i=0;i<size_of_second;i++)
{
ans=first_value[size_of_first - i-1] + second_value[size_of_second-i-1] + carry -'0';
carry=0;
if (ans > '9')
{
carry = 1;
result[biggest_size - i]= ans - 10;
}
else
{
result[biggest_size - i] = ans;
}
}
if(!carry) //since there is an option that there
//will be no borrow i will cp it.
{
for(i = 0;i < delta; i++)
{
result[biggest_size - size_of_second - i] =
first_value[size_of_first - size_of_second - i- 1];
}
}
if (carry)
{
for (i = 0;i < (delta) ;i++)
{
ans=first_value[size_of_first - size_of_second - i - 1] + carry;
carry = 0;
if (ans > '9')
{
carry = 1;
result[biggest_size-size_of_second - i] = ans - 10 ;
}
else
{
result[biggest_size - size_of_second - i] = ans ;
}
}//end of for
if (carry)
{
result[0]='1';
}
}//end of if (exsitence of an carry
return result;
}
the first thing you need is to create a function that returns the integer value of a char:once you have this we can work out the next step, which would be to figure out how to convert between your two 'languages' (ie string and integers).Code:int char2int(char c);
some examples (note that you would already have a way to convert a char to an int, so everything is represented using ints):
1 = 10^0 * 1
2 = 10 ^0 * 2
10 = 10^1 * 1
15 = 10^1 * 1 + 10^0 *5
@jabka Please don't post stuff like that, He has to do the work, it's his homework.
Also you've posted C++ code in the C section...
Characters already have an integer value. They're also nicely sequenced, so all you have to do is subtract the value of the character zero from one to see if it's zero through nine. I can see if you just enjoy over complicating things, but it's hardly needed here.Quote:
Originally Posted by nadroj
Quzah.
i know they have a character value, and im not trying to overcomplicate things. what if the character is 'z' this would screw up though, right?
That's what error checking is for. You could always just use isdigit.Code:signed int x = 'z' - '0';
if( x < 0 || x > 9 )
puts( "You didn't enter a digit." );
Quzah.
im assuming he cant use functions like that, but i was still waiting for the answer from my previous post.
You don't need a function for it. Just basic subtraction, as I mentioned. Actually, you don't even need subtraction for digit testing. All you have to do is compare it to the range of zero to nine as a character.
Quzah.
ok sounds fair. either way would work. i just never thought about the ascii characters.
edit:something like this?:Quote:
All you have to do is compare it to the range of zero to nine as a character.
if thats the case, then thats exactly what i was thinking of to make a function. or you could just do it in the loop that hell need in the final product, but id just like to seperate this.Code:if (myChar == '1')
myDigit = 1;
//etc
sorry if i do some thing wrong posting that code ..
anyway ..
as have been said before there are more then two ways to aproach this :
1. to convert the strings to int then do math stuff on it;
2. to work on strings (like i did);
3. more options .
if you prefear to work with numbers and not chars
[Qoute]
(int) char_varibale
[/Qoute]
but be aware that numbers more then 32K will have to be dobule and not int.
so you probably will need to some cutting on the string
look on what i posted and work around that.
p.s.
sorry if i misspell something (i don't know how to make my gcc warn my about English syntax errors ).
better will be :Quote:
Originally Posted by quzah
Code:if !((x[i] >= '0') && (x[i ]<= '9'))
printf("sorry mate but you have enterd a non digit value %c\n",x[i]);
A typecast won't make a '9' into a 9.
Quzah.
both ways will work.Quote:
Originally Posted by jabka
Even better would be if your example actually compiled. But we'll pretend it's a typo.Quote:
Originally Posted by jabka
Quzah.
quzah can you comment on post 15? thanks
edit: nevermind, i think what you mentioned was similar to what was just discussed. wow i am not thinking tonight.
@nadroj,
quzah said to do error checking in that manor, not comparing each ascii character in a control then setting a variable to it's corresponding value.
Doing it the way you mention'd is rather crappy, considering if you had to do upto 255 comparisons.
my bad lost the braces before the not ..Quote:
Originally Posted by quzah
here is the compiled form ..
Code:#include <stdio.h>
int main(){
int i=0;
char x[10] = {'0','1','2','a','4','5','6','7','8','x'};
for (i = 0;i < 10; i++)
if (!((x[i] >= '0') && (x[i] <= '9')))
printf("non digit on : %d \n",i);
}
of course you wouldnt have to do 255 comparisons. you compare 0 to 9.
Who said you wouldn't?
If someone also wanted to allow the alphabet thats another 26 or 52 , but then they wanted to allow some special chars, its another n chars... It'd become very messy and bloated
what we were discussing is how to convert the char to a number. the (poor) way that i was thinking to do it is you compare the character to each character '0' to '9', 10 comparisons. nothing about 255 comparisons or the alphabet. but i already know this is a efficient way to go.
Yes I am aware of that, but every line of code you write should keep future modification in mind, especially if you work in a group.
However a look-up table could be considered a crude universal way of solving the problem, one may even call it a 'hack'.
initially i said what i was going to do was going to be in a function, 'char2int'. which had that one purpose, so it wouldnt require future modification. but i agree that it is good practice to keep that in mind.
edit: in the event that mathematicians invent a new number, id be screwed though!
If you're going to worry about future modifications, then a lookup table is a lousy way to go, since it would be locale specific.Quote:
Originally Posted by zacs7
Quzah.