copying a substring from a string given end index in string

Question

Hi,

How can i copy a substring from a given string with start and end index or giving the start index and length of the string are given.

Thanks, iSight

Answer 1

From a std::string? std::string::substr will create a new std::string from an existing one given a start index and a length. It should be trivial to determine the necessary length given the end index (although it will depend on whether the end index is inclusive or exclusive).

If you're trying to create a substring from a C-style string (a NUL-terminated char array), then you can use the std::string(const char* s, size_t n) constructor. For example:

const char* s = "hello world!";
size_t start = 3;
size_t end = 6; // Assume this is an exclusive bound.

std::string substring(s + start, end - start);

Answer 2

std::string thesub = thestring.substr(start, length);

or

std::string thesub = thestring.substr(start, end-start+1);

assuming you want the endth character to be included in the substring.

Answer 3

You can use substr method od std:string class.