Problem about the return value type of generic algorithm find().

nanchuangyeyu · #1 09-Jul-2009, 07:01

Hi,
I know the return value of generic search algorithm "find()" is of iterator type. Now how can I output the return value as numeric type? For example:

CPP / C++ / C Code:

short myArray[4] = {2,1,3,7};
vector<short>mVec(myArray,myArray+4);
vector<short>::iterator found;
found = find(mVec.begin(),mVec.end(),2);

In this code the variable found will be assigned the "mVec.begin", but can I obtain its numeric counter part,say, 0 instead? How? Thank u in advance.

L7Sqr · #2 09-Jul-2009, 07:12

Are you looking to get the index at which the element was found? Or are you looking to get the value of an iterator? I'll assume the former since by virtue of having the iterator and search term you already have all the ingredients for the latter.
I dont know that there is a direct way to do that with the iterator without keeping an index and comparing each element in the vector. If that is the case, you may be better off just iterating over the vector by hand anyway.

LuciWiz · #3 09-Jul-2009, 07:21

You can dereference the returned iterator:

CPP / C++ / C Code:

std::cout << *found << std::endl;

Best regards,
Lucian

LuciWiz · #4 09-Jul-2009, 07:28

Quote:

Originally Posted by L7Sqr

Are you looking to get the index at which the element was found? Or are you looking to get the value of an iterator? I'll assume the former since by virtue of having the iterator and search term you already have all the ingredients for the latter.
I dont know that there is a direct way to do that with the iterator without keeping an index and comparing each element in the vector. If that is the case, you may be better off just iterating over the vector by hand anyway.

After reading your post I realize the OP was probably asking about the numeric index.
You can subtract iterators in a vector:

CPP / C++ / C Code:

std::cout << "Found 2 at index : " << found - mVec.begin() << std::endl;

Of course, the proper checks should be made (std::find will return end if it can't find the item).

Best regards,
Lucian

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Problem about the return value type of generic algorithm find().

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