Converting string to int in C++

[Juggernautilus]

Hi, I have been learning C++ for a while now but never I had to do this.

 

I am practising for programming contest at my school and I will have to read and write from files.

 

In the file I read, I have a string with 6 numbers, all seperated by a space. So far I got the code to get seperate strings of these numbers. For example: "1" "2" "3" "4" "5" "6" or "1213" "423412" etc.

I will not get into details what I have to do further, because I have it done already. All I need to know how to convert these strings of numbers to integers. 

 

Also, the max size of the number is 10¹⁸ so they will surely use at least one max number. Should I use long int or int is fine?

 

 

Sorry for my terrible English

[MatazaNZ]

The max size for int is 65,536, if that helps

[dragosudeki]

Could take the substring of the leftmost character and then examine the ASCII or whatever value for it (can be determined by assigning to an integer) and find out the actual integer value from that. Then if there is another character take what you have found out and just multiply by 10 and continue. I won't write any code for you, but that is the general idea.

[fizzlesticks]

The max size for int is 65,536, if that helps

You're off by about 15 powers of 2.

[Mo5]

Use method atoi();

 

 

atoi()

Prototype: int atoi(const char *string);
Header File: stdlib.h © or cstdlib (C++)
Explanation: This function accepts a string and converts it into an integer. For example, if "1234" is passed into the function, it will return 1234, an integer. If the string contains a decimal place, the number will be truncated. Eg, "104.21" will be returned as 104.

Source: http://www.cprogramming.com/fod/atoi.html

[Juggernautilus]

Use method atoi();

Source: http://www.cprogramming.com/fod/atoi.html

Thanks this is just what I needed

[Rup-Inc]

There is also std::stoi and others if you need more control and are using c++11.

[DavidTheWin]

The max size for int is 65,536, if that helps

 

I don't think there are any languages that implement max signed int as anything other than 2^31-1

[MatazaNZ]

You're off by about 15 powers of 2.

I though int was 16 bit?

[madknight3]

I don't think there are any languages that implement max signed int as anything other than 2^31-1

Yeah, what he said is an unsigned short (unsigned 16 bit int).

 

 

I though int was 16 bit?

It still isn't unsigned by default though even if it is. And I think it's 32 bit default these days but I could be wrong.