How to compare two vectors for equality element by element in C

Question

Is there any way to compare two vectors   if  vector1    vector2      DoSomething      Note  Currently  these vectors are not sorted and contain integer values

User · Answer

If they really absolutely have to remain unsorted (which they really don't.. and if you're dealing with hundreds of thousands of elements then I have to ask why you would be comparing vectors like this), you can hack together a compare method which works with unsorted arrays.

The only way I though of to do that was to create a temporary vector3 and pretend to do a set_intersection by adding all elements of vector1 to it, then doing a search for each individual element of vector2 in vector3 and removing it if found. I know that sounds terrible, but that's why I'm not writing any C++ standard libraries anytime soon.

Really, though, just sort them first.

User · Answer

Check  std  mismatch method of C     comparing vectors has been discussed on DaniWeb forum and also answered   C    Comparing two vectors  Check the below SO post  will helpful for you  they have achieved the same with different-2 method   Compare two vectors C

User · Answer

C  11 standard on    for std  vector Others have mentioned that operator   does compare vector contents and works  but here is a quote from the C  11 N3337 standard draft which I believe implies that  We first look at Chapter 23 2 1  quot General container requirements quot   which documents things that must be valid for all containers  including therefore std  vector  That section Table 96  quot Container requirements quot  which contains an entry   Expression   Operational semantics                                     a    b       distance a begin    a end       distance b begin    b end     amp  amp               equal a begin    a end    b begin      The distance part of the semantics means that the size of both containers are the same  but stated in a generalized iterator friendly way for non random access addressable containers  distance   is defined at 24 4 4  quot Iterator operations quot   Then the key question is what does equal   mean  At the end of the table we see   Notes  the algorithm equal   is defined in Clause 25   and in section 25 2 11  quot Equal quot  we find its definition   template lt class InputIterator1  class InputIterator2 gt  bool equal InputIterator1 first1  InputIterator1 last1             InputIterator2 first2    template lt class InputIterator1  class InputIterator2  class BinaryPredicate gt  bool equal InputIterator1 first1  InputIterator1 last1             InputIterator2 first2  BinaryPredicate pred    1 Returns  true if for every iterator i in the range  first1 last1  the following corresponding conditions hold   i      first2    i - first1    pred  i    first2    i - first1       false  Otherwise  returns false   In our case  we care about the overloaded version without BinaryPredicate version  which corresponds to the first pseudo code definition  i      first2    i - first1    which we see is just an iterator-friendly definition of  quot all iterated items are the same quot   Similar questions for other containers   how to compare two std  set

User · Answer

Your code  vector1    vector2  is correct C   syntax  There is an    operator for vectors   If you want to compare short vector with a portion of a longer vector  you can use theequal   operator for vectors   documentation here   Here s an example   using namespace std   if  equal vector1 begin    vector1 end    vector2 begin          DoSomething

User · Answer

According to the discussion here you can directly compare two vectors using           if  vector1    vector2        true   else       false

[c++] How to compare two vectors for equality element by element in C++?

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