The most fundamental problem of your test application is that you call srand once and then call rand one time and exit. The whole point of srand function is to initialize the sequence of pseudo-random numbers with a random seed. It means that if you pass the same value to srand in two different applications (with the same srand/rand implementation) then you will get exactly the same sequence of rand() values read after … Read more
It won’t automatically convert (thank god). You’ll have to use the method c_str() to get the C string version. Note that it returns a const char *; you aren’t allowed to change the C-style string returned by c_str(). If you want to process it you’ll have to copy it first: Or in modern C++:
Simple: The Standard Library comes with a nice collection of built-in exception objects you can throw. Keep in mind that you should always throw by value and catch by reference: You can have multiple catch() statements after each try, so you can handle different exception types separately if you want. You can also re-throw exceptions: … Read more
As it is, both dimensions of your vector are 0. Instead, initialize the vector as this: This will give you a matrix of dimensions RR * CC with all elements set to 0.
The problem C++ includes useful generic functions like std::for_each and std::transform, which can be very handy. Unfortunately they can also be quite cumbersome to use, particularly if the functor you would like to apply is unique to the particular function. If you only use f once and in that specific place it seems overkill to … Read more
From the cplusplus.com page about the begin member function of unordered_map (link): Notice that an unordered_map object makes no guarantees on which specific element is considered its first element. So no, there is no guarantee the elements will be iterated over in the order they were inserted. FYI, you can iterate over an unordered_map more … Read more
This line doesn’t do the right thing: You want to count by 32, that’s either or I strongly recommend making the numeric and character values match during your output. So change to
One method would be to use the array to initialize the vector
This is not related to performance at all. But consider this: you are using two libraries called Foo and Bar: Everything works fine, and you can call Blah() from Foo and Quux() from Bar without problems. But one day you upgrade to a new version of Foo 2.0, which now offers a function called Quux(). … Read more
Huge difference. As the name implies, a double has 2x the precision of float[1]. In general a double has 15 decimal digits of precision, while float has 7. Here’s how the number of digits are calculated: double has 52 mantissa bits + 1 hidden bit: log(253)÷log(10) = 15.95 digits float has 23 mantissa bits + … Read more