c++11 - perplexing things in c++ -

i trying copy array of chars, other array of chars in reversed order.

this method:

void reversstring(char* str){     char* ptr = str;      int = 0;     // getting length of str/ptr array     while (*(ptr + i) != '\0'){         = + 1;     }      char revstr [i];     char * revstrchar = &revstr[0];     int revstrpos = 0;      cout << *(ptr + 3) << endl;  } 

here trying copy in normal order, if print last letter of input ("abcd"), nothings happens. prints empty line.

but if delete declaration of new char array:

void reversstring(char* str){     char* ptr = str;      int = 0;     // getting length of str/ptr array     while (*(ptr + i) != '\0'){         = + 1;     }      //char revstr [i];     //char * revstrchar = &revstr[0];     //int revstrpos = 0;      cout << *(ptr + 3) << endl;  } 

then prints last letter correctly, "d". not understand how declaring new char array influences output! (compiler mingw, os win10)

you tagged c++11 . . . why not more modern stl way:

#include <iostream> #include <string> #include <algorithm>   int main() {    std::string str{"12345abc"};    std::string copy = str;    std::reverse(copy.begin(), copy.end());     std::cout << copy << std::endl;     return 0; } 

output:

cba54321