How do I reverse a C vector

Question

Is there a built-in vector function in C   to reverse a vector in place   Or do you just have to do it manually

User · Accepted Answer

There s a function std  reverse in the algorithm header for this purpose    include  lt vector gt   include  lt algorithm gt   int main       std  vector lt int gt  a    std  reverse a begin    a end       return 0

User · Answer

include lt algorithm gt   include lt vector gt   include lt iostream gt  using namespace std  int main         vector lt int gt v1      for int i 0  i lt 5  i            v1 push back i 2       for int i 0  i lt v1 size    i            cout lt  lt v1 i        02468     reverse v1 begin   v1 end              for int i 0  i lt v1 size    i            cout lt  lt v1 i       86420

User · Answer

You can also use std  list instead of std  vector  list has a built-in function list  reverse for reversing elements

User · Answer

All containers offer a reversed view of their content with rbegin   and rend    These two functions return so-calles reverse iterators  which can be used like normal ones  but it will look like the container is actually reversed    include  lt vector gt   include  lt iostream gt   template lt class InIt gt  void print range InIt first  InIt last  char const  delim     n      --last    for   first    last    first       std  cout  lt  lt   first  lt  lt  delim        std  cout  lt  lt   first     int main      int a       1  2  3  4  5      std  vector lt int gt  v a  a 5     print range v begin    v end     - gt       std  cout  lt  lt    n              n     print range v rbegin    v rend      lt -        Live example on Ideone  Output   1- gt 2- gt 3- gt 4- gt 5               5 lt -4 lt -3 lt -2 lt -1

User · Answer

Often the reason you want to reverse the vector is because you fill it by pushing all the items on at the end but were actually receiving them in reverse order  In that case you can reverse the container as you go by using a deque instead and pushing them directly on the front   Or you could insert the items at the front with vector  insert   instead  but that would be slow when there are lots of items because it has to shuffle all the other items along for every insertion   So as opposed to   std  vector lt int gt  foo  int nextItem  while  getNext nextItem         foo push back nextItem     std  reverse foo begin    foo end       You can instead do   std  deque lt int gt  foo  int nextItem  while  getNext nextItem         foo push front nextItem        No reverse needed - already in correct order

User · Answer

You can use std  reverse like this  std  reverse str begin    str end

[c++] How do I reverse a C++ vector?

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