How to repeat a string a variable number of times in C

Question

I want to insert  n  spaces  or any string  at the beginning of a string in C    Is there any direct way to do this using either std  strings or char  strings   E g  in Python you could simply do   gt  gt  gt        5    lolcat        lolcat

User · Answer

For the purposes of the example provided by the OP std  string s ctor is sufficient  std  string 5        However  if anybody is looking for a function to repeat std  string multiple times   std  string repeat const std  string amp  input  unsigned num        std  string ret      ret reserve input size     num       while  num--          ret    input      return ret

User · Answer

I know this is an old question  but I was looking to do the same thing and have found what I think is a simpler solution  It appears that cout has this function built in with cout fill    see the link for a  full  explanation  http   www java-samples com showtutorial php tutorialid 458  cout width 11   cout fill       cout  lt  lt   lolcat   lt  lt  endl    outputs       lolcat

User · Answer

There s no direct idiomatic way to repeat strings in C   equivalent to the   operator in Python or the x operator in Perl  If you re repeating a single character  the two-argument constructor  as suggested by previous answers  works well   std  string 5         This is a contrived example of how you might use an ostringstream to repeat a string n times    include  lt sstream gt   std  string repeat int n        std  ostringstream os      for int i   0  i  lt  n  i            os  lt  lt   repeat       return os str        Depending on the implementation  this may be slightly more efficient than simply concatenating the string n times

User · Answer

You should write your own stream manipulator  http   www two-sdg demon co uk curbralan papers WritingStreamManipulators html  cout  lt  lt  multi 5   lt  lt   quot whatever quot   lt  lt   quot lolcat quot

User · Answer

Use one of the forms of string  insert   std  string str  lolcat    str insert 0  5          This will insert          five dots  at the start of the string  position 0

User · Answer

ITNOA  You can use C   function for doing this    std  string repeat const std  string amp  input  size t num         std  ostringstream os      std  fill n std  ostream iterator lt std  string gt  os   num  input       return os str

User · Answer

In the particular case of repeating a single character  you can use std  string size type count  CharT ch    std  string 5          lolcat    NB  This can t be used to repeat multi-character strings

User · Answer

Here s an example of the string  quot abc quot  repeated 3 times   include  lt iostream gt   include  lt sstream gt   include  lt algorithm gt   include  lt string gt   include  lt iterator gt   using namespace std   int main         ostringstream repeated      fill n ostream iterator lt string gt  repeated   3  string  quot abc quot         cout  lt  lt   quot repeated   quot   lt  lt  repeated str    lt  lt  endl      repeated  abcabcabc     return 0

User · Answer

As Commodore Jaeger alluded to  I don t think any of the other answers actually answer this question  the question asks how to repeat a string  not a character   While the answer given by Commodore is correct  it is quite inefficient  Here is a faster implementation  the idea is to minimise copying operations and memory allocations by first exponentially growing the string    include  lt string gt   include  lt cstddef gt   std  string repeat std  string str  const std  size t n        if  n    0            str clear            str shrink to fit            return str        else if  n    1    str empty              return str            const auto period   str size        if  period    1            str append n - 1  str front             return str            str reserve period   n       std  size t m  2       for    m  lt  n  m    2  str    str      str append str c str     n -  m   2     period       return str      We can also define an operator  to get something closer to the Python version    include  lt utility gt   std  string operator  std  string str  std  size t n        return repeat std  move str   n       On my machine this is around 10x faster than the implementation given by Commodore  and about 2x faster than a naive  append n - 1 times  solution

[c++] How to repeat a string a variable number of times in C++?

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