char-pointer

I want to create a C program to generate numbers from 0 to 999999, keeping in mind that the number generated should not have any digits that are repetitive within it. For example, "123" is an acceptable value but not "121" as the '1' is repeated. I have sourced other program codes that check if an integer has repeated digits: Check if integer has repeating digits. No string methods or arrays What is the fastest way to check for duplicate digits of a number? However these do not really solve my problem and they are very inefficient solutions if I were to perform the check for 1,000,000

Code: #include <stdio.h> int main() { char *str; char i = 'a'; str = &i; str = "Hello"; printf("%s, %c, %x, %x", str, i, str, &i); return 0; } I get this output: Hello, a, 403064, 28ff0b I have following two doubts: How can I store a string without allocating any memory for it. str is a character pointer and is pointing to where char variable i . When I add str = "Hello"; aren't I using 5 bytes from that location 4 of which are not allocated? Since, I code str = &i; shouldn't str and &i have same value when I printf them? When I remove the str = "Hello"; statement str and &i are same. And if

I have an API function that expects a char*** parameter and want to pass a vector<std::string> . Are there member functions of std::string that let me do that? This way, I only get the char pointer to the first element: std::vector<std::string> oList(128); myFunction(oList[0].c_str()); "Are there member functions of std::string that let me do that?" In short: No. That std::vector<std::string> stores the std::string instances in a contiguous array, doesn't mean that the pointers to the underlying char arrays of these string instances appear contiguously in memory. There is no way to cast the

I answered a question here: https://stackoverflow.com/a/28862668/2642059 Where I needed to use recurrence to step through a string . I wanted to use a const string& as my parameter on each function, but unless I wanted to reconstruct the string each recursion I found that I needed to pass a start and finish position as well as the string itself. So it became pointless to pass the string at all. In the end I choose to just pass a start and finish pointer to the char[] . As an example, say that I'm given a string which contains nested parenthesis (but no side by side parenthetical insertions.)

Why does the following assignment not work? I would like a low-level explanation if possible. Also, here's the compiler error I get: incompatible types in assignment of 'char*' to 'char [20]' class UCSDStudent { char name[20]; public: UCSDStudent( char name[] ) { //this-> name = name; does not work! Please explain why not strcopy( this -> copy, copy ); //works } }; Because when you have a function call like this UCSDStudent( char name[] ) only the adress of the array name is copied instead of the whole array. It is a C\C++ feature. Furthermore the name defined as char name [20] is not a