STL source code profiling algorithm stl_algo.h -- random_shuffle

STL source code profiling algorithm stl_algo.h -- random_shuffle

 

Random_shuffle

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Description: sorts the elements of [first, last) at random.
Ideas:
Must be RandomAccessIterator
1. Traverse intervals
2. Generate a random number rand in [0, I) and exchange * (first + rand) with I.
?? How to prove randomness
Source code:

Template
 
  
Inline void random_shuffle (RandomAccessIterator first, RandomAccessIterator last) {_ random_shuffle (first, last, distance_type (first);} template
  
   
Void random_shuffle (RandomAccessIterator first, RandomAccessIterator last, RandomNumberGenerator & rand) {// The parameter must be referenced here. Because the random number generator has a local state, if (first = last) return; for (RandomAccessIterator I = first + 1; I! = Last; ++ I) iter_swap (I, first + rand (I-first) + 1);} template
   
    
Void _ random_shuffle (RandomAccessIterator first, RandomAccessIterator last, Distance *) {if (first = last) return; for (RandomAccessIterator I = first + 1; I! = Last; ++ I) # ifdef _ STL_NO_DRAND48 iter_swap (I, first + Distance (rand () % (I-first) + 1 ))); # else iter_swap (I, first + Distance (lrand48 () % (I-first) + 1); # endif}
   
  
 

Example:

int main(){vector
 
   vec;for(int ix = 0; ix < 10; ix++)vec.push_back(ix);random_shuffle(vec.begin(), vec.end());copy(vec.begin(), vec.end(), ostream_iterator
  
   (cout,  ));}