how do I get a part of the a string in C++

Question

I am just wondering how do I get a part of a string in C++, like I want to know what are the elements from 0 to i. Thanks.

Answer 1

You want to use std::string::substr. Here's an example, shamelessly copied from http://www.cplusplus.com/reference/string/string/substr/

// string::substr
#include <iostream>
#include <string>
using namespace std;

int main ()
{
  string str="We think in generalities, but we live in details.";
                             // quoting Alfred N. Whitehead
  string str2, str3;
  size_t pos;

  str2 = str.substr (12,12); // "generalities"

  pos = str.find("live");    // position of "live" in str
  str3 = str.substr (pos);   // get from "live" to the end

  cout << str2 << ' ' << str3 << endl;

  return 0;
}

Answer 2

You use substr, documented here:

#include <iostream>
#include <string>
using namespace std;
int main(void) {
    string a;
    cout << "Enter string (5 characters or more): ";
    cin >> a;
    if (a.size() < 5)
        cout << "Too short" << endl;
    else
        cout << "First 5 chars are [" << a.substr(0,5) << "]" << endl;
    return 0;
}

You can also then treat it as a C-style string (non-modifiable) by using c_str, documented here.

Answer 3

if u mean string is an array of characters,

char str[20];
int i;
strcpy(str,"Your String");

//Now lets get the substr
cin>>i;

// do some out-of-bounds validation here if u want..
str[i+1]=0;
cout<<str;

if u mean the std::string use substr function.. as Will suggested

Answer 4

Assuming you're using the C++ std::string class

you can do:

std::string::size_type start = 0;
std::string::size_type end = 1; //don't use int. Use size type for portability!
std::string myStr = "hello";
std::string sub = myStr.substr(start,end);
std::cout << sub; //should print h