C vector of char array

Question

I am trying to write a program that has a vector of char arrays and am have some problems   char test         a    b    c    d    e      vector lt char   gt  v   v push back test     Sorry this has to be a char array because I need to be able to generate lists of chars as I am  trying to get an output something like   a a a b a c a d a e b a b c  Can anyone point me in the right direction   Thanks

User · Answer

You can use boost  array to do that   boost  array lt char  5 gt  test     a    b    c    d    e    std  vector lt boost  array lt char  5 gt   gt  v  v push back test     Edit   Or you can use a vector of vectors as shown below   char test       a    b    c    d    e    std  vector lt std  vector lt char gt   gt  v  v push back std  vector lt char gt  test  test   sizeof test   sizeof test 0

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What I found out is that it s OK to put char  into a std  vector       1 - A std  vector of char   more preper way is to use a std  vector lt std  vector lt char gt  gt  or std  vector lt std  string gt  std  vector lt char  gt  v 10   hi            You cannot put standard library containers e g  char   into std  vector  for  auto amp  i   v          std  cout  lt  lt  i  lt  lt  std  endl      i    New     for  auto i   v        std  cout  lt  lt  i  lt  lt  std  endl

User · Answer

You cannot store arrays in vectors  or in any other standard library container   The things that standard library containers store must be copyable and assignable  and arrays are neither of these   If you really need to put an array in a vector  and you probably don t - using a vector of vectors or  a vector of strings is more likely what you need   then you can wrap the array in a struct   struct S     char a 10        and then create a vector of structs   vector  lt S gt  v  S s  s a 0     x   v push back  s

User · Answer

Use std  string instead of char-arrays   std  string k   abcde   std  vector lt std  string gt  v  v push back k

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FFWD to 2019  Although this code worketh in 2011 too      g   prog cc -Wall -std c  11  include  lt iostream gt   include  lt vector gt    using namespace std    template lt size t N gt      inline        constexpr    compile time          array lt char N gt  string literal to array   char const   amp charrar  N           return std  to array  charrar         template lt size t N gt      inline           run time          vector lt char gt  string literal to vector   char const   amp charrar  N           return   charrar  charrar   N         int main        constexpr auto arr   string literal to array  Compile Time       auto cv   string literal to vector   Run Time        return 42      Advice  try optimizing the use of std  string  For char buffering std  array lt char N gt  is the fastest  std  vector lt char gt  is faster    https   wandbox org permlink wcasstoY56MWbHqd

User · Answer

You can directly define a char type vector as below   vector lt char gt  c     a    b    c    vector  lt  vector lt char gt   gt  t      a   a     b   b

User · Answer

You need  char test      abcde       This will add a terminating  0 character to the array std  vector lt std  string gt  v  v push back test     Of if you meant to make a vector of character instead of a vector of strings   std  vector lt char gt  v test  test   sizeof test  sizeof  test      The expression sizeof test  sizeof  test  is for calculating the number of elements in the array test

User · Answer

In fact technically you can store C   arrays in a vector  and it makes a lot of sense  Not directly  but by a simple workaround  wrapping in a class  will meet exactly all the requirements of a multidimensional array  As the question is already answered by anon  Some explanations steel needed  STL already provides std  array for these purposes  Is an unpleasant surprise to fall in the trap of not understanding clearly the difference between arrays and pointers  between multidimensional arrays and arrays of arrays  and so on and so on  Vectors of vectors contains vectors as elements  Each element containing a copy of size  capacity and maybe other things  meanwhile the vector datas for elements will be placed in different random places in memory  But a vector of arrays will contain a contiguous segment of memory with all data  which is identical to multidimensional array  Also there is no good reason to keep the size of each array element while it is known to be the same for all elements  So  making a vector of array  you can t do it directly  But you can workaround it easily by wrapping the array in a class  and in this sample the memory will be identical to the memory of a bidimensional array  This approach is already widely used by many libraries  At low level it will be easily interoperable with APIs that are not C   vector aware  So without using std  array it will look like this  int main         struct ss               int a 5           int amp  operator    const int amp  i    return a i           a  1 2 3 4 5    b  9 8 7 6 5         vector lt ss gt  v      v resize 10       v 0    a      v 1    b      v push back a      will push to index 10  with reallocation     v push back b      will push to index 11  with reallocation      auto d   v data           cin  gt  gt  v 1  3     input any element from stdin     cout  lt  lt   quot show two element   quot  lt  lt  v 1  2   lt  lt  quot   quot  lt  lt  v 1  3   lt  lt  endl      return 0     Since C  11 STL contains std  array for these purposes  so no need to reinvent it        include lt array gt       int main         vector lt array lt int  5 gt  gt  v      v reserve 10       v resize 2       v 0    array lt int  5 gt   1  2  3  4  5       v 1    array lt int  5 gt   9  8  7  6  5       v emplace back array lt int  5 gt   7  2  53  4  5            cin  gt  gt  v 1  1       auto d   v data     Now look how looks in memory  Now  this is why vectors of vectors is not the answer  Supposing following code int main         vector lt vector lt int gt  gt  vv       1 2 3 4 5      9 8 7 6 5          auto dd   vv data        return 0     Guess what it looks like in the memory now

[c++] C++ vector of char array

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