Cannot convert from string to hexadecimal

Question

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C++ convert hex string to signed integer

I have the string line which is a hexadecimal number say like 12ab43c..(but I have read it as a string) and I would like to pass it to an unsigned char* linehex or directly to a hexadecimal so I can later use it in my program for further computations. Which is the most efficient way to do this?

Check out the [`strtol`](http://en.cppreference.com/w/cpp/string/byte/strtol) function. — Some programmer dude, Sep 24 '12 at 15:38

score 3 · Answer 1 · answered Sep 24 '12 at 15:42

The easiest is probably to read it as a number to start with, instead of reading it as a string, then converting. For example:

some_stream >> std::hex >> your_number;

Quick demo code:

#include <iostream>

int main() {    
    int x;

    std::cin >> std::hex >> x;

    std::cout << x << "\n";
    return 0;
}

Input: ff
Output: 255

Cannot convert from string to hexadecimal

1 Answers1