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Is there any difference in output behaviour between using size(x) instead of x.size(), where x is a string variable? Or it is just another alias?
The behavior of std::size is:
Returns the size of the given container c or array array.
1-2) Returns c.size(), converted to the return type if necessary.
...
So calling std::size(x) and x.size() has the same effect, where x is a std::string.
(This function can also accept an array, but that's not relevant when it comes to a std::string).
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What is npos ??? I recently saw it in some source code and really want to know what it is used for and why it is used. An example would be nice also. Thanks(:
The documentation says :
npos is a static member constant value with the greatest possible
value for an element of type size_t
This value, when used as the value for a len (or sublen) parameter
in string's member functions, means "until the end of the string".
As a return value, it is usually used to indicate no matches.
It is defined internally as :
static const size_t npos = -1;
Just remember, it's used to indicate not found.
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I am looking for a function to compare the two strings. A functional similar to strcmp in CString with the difference that takes two strands in the input.
You can use std::string::compare (it returns 0 if values are the same). Also be aware that in fact you can use strcmp in c++, but if you want modern c++ version i would go with std::string::compare.
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Why LOG and 0 are used in this statement?
LOG = 35;
vector<int> cnt(LOG, 0); //here cnt is a vector name
The statement is constructing a std::vector, so you should look at help documentation for the vector constructor.
In this case, LOG and 0 are being used specifically in the two-parameter override of the constructor.
LOG is used to specify the initial size of the vector;
0 is used to specify the initial value of the elements.
In other words, the expression declares a vector named cnt being of size 35 with all elements initialized to 0.
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When I print the default value of array on heap memory I'm getting random big numbers in code block. I know that the default value of array is 0 but I am getting random number .
The doc of the std::array constructor says it:
initializes the array following the rules of aggregate initialization (note that default initialization may result in indeterminate values for non-class T)
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I tried to Google but in vain.
In C++ arrays are stored in contiguous memory.
This means that if you have an element x and you know that it's inside an array and that it's not the first element of the array, then then previous one is
*(&x - 1)
i.e. the element pointed by the address of x after we subtract 1 (note that this works because pointer arithmetic in C++ considers element size, so &x - 1 is not point to the byte before, but to the element before).