Converting a String to an Integer

1. Modify your previous exercise for sorting vector elements. This time, after reading a string of digits, we want to convert it into an integer, and store these numbers in an integer vector.
2. To convert a character array to an integer, you may use the atoi() function.
   • If you store the input number in a character array (e.g. char s[10]), you can simply pass it as an argument to atoi().
   • If you store the input line in a string object (e.g. string s), atoi() cannot handle this data type because a string is essentially different from a character array. You need to invoke a member function c_str() of the string class to convert it to a character array first, and pass it to atoi() like this:
     • n = atoi( s.c_str() );
3. The sorting result should look like this:

   
   Please input file name -- vector1.dat
   
   1:      7
   2:      9
   3:      14
   4:      15
   5:      17
   6:      18
   7:      20
   8:      23
   9:      24
   10:     32
   11:     40
   12:     41
   13:     45
   14:     54
   15:     55
   16:     58
   17:     63
   18:     66
   19:     78
   20:     84