C++ for Scientists - Technische Universität Dresden

2.12. EXERCISES 63
The first line that does not start with % contains the number of rows, the number of columns
and the number of non-zero elements on the sparse matrix.
Use fstream to read the header of a MatrixMarket file and print the number of rows and columns,
and the number of nonzeroes on the screen.
2.12.5 String manipulation programs
There is a type string in the standard library. This type contains a large number of string
operations, such as string concatenation, string comparison, etc. Note the include of the header
file string.
#include
#include
int main()
{
std::string s1 = ”Hello”;
std::string s2 = ”World”;
std::string s3 = s1 + ”, ” + s2 ;
std::cout ≪ s3 ≪ std::endl ;
return 0;
}
In this example we have concatenated the strings s1 and s2 together with a string constants.
Perform the following exercises:
1. Write a function itoa (int i, std::string& b) that constructs a string representation of i in b
and returns b.
2. Write a simple encryption program. It should read the input from cin and write the
encrypted symbols in cout. Use the following simple encryption scheme: the code for a
symbol c is c key[i] , where key is a string given as a parameter to a function. The symbols
from key are used in a cyclic way. (After the repeated encryption with a same key key you
should get the source string.)