Std::shuffle-c++

In Python we often see Shuffle's random permutation function, which can randomly arrange the contents of a list, but in C + + you need to implement functions like this (c++0x). After c++0x, such function functions have a corresponding--std::shuffle in the standard library. The following is a specific description of the function: [CPP]View PlainCopy 

1. Template <class Randomaccessiterator, class urng>
2. void Shuffle (Randomaccessiterator first, Randomaccessiterator last, urng&& g);

function function: Use random generator g to randomly arrange the inner elements of an element [first, last] feasible exchange, presumably similar to the following code functions [CPP]View PlainCopy 

1. template < Class randomaccessiterator, CLASS&NBSP;URNG>&NBSP;&NBSP;
2. void shuffle  (randomaccessiterator first,  RANDOMACCESSITERATOR&NBSP;LAST,&NBSP;URNG&&&NBSP;G)   
3. {   
4.   for  (auto i =  (Last-first)  - 1;  i > 0; --i)  {  
5. &NBSP;&NBSP;&NBSP;&NBSP;STD: : Uniform_int_distribution<decltype (i) > d  (0,i);   
6.      swap  (first[i], first[d  (g)]);   
7. &NBSP;&NBSP;}&NBSP;&NBSP;
8. }  

The function must be used with the default random generator of the standard library, and the header file of the random generator is <random>. You can refer to the Random_shuffle function if you want to use a random generator function that does not need to be passed in.

Parameters:

First

, the beginning (begin) and end (end) of the last sequential container iterator, the values in the interval of [first, end] will be randomly sorted. The iterator for the sequential container must be the data type that defines the swap function and the order container must also support the element to be exchanged. An instance of the G unique random number generator, defined in header file <random>. URNGis the abbreviation for uniform random number generator.

return value:

None

Case: [CPP]View PlainCopy 

2. #include <iostream>
4. #include <vector>
6. #include <algorithm>//Std::move_backward
8. #include <random>/std::d efault_random_engine
10. #include <chrono>//Std::chrono::system_clock
14. int main (int argc, char* argv[])
16. {
18. std::vector<int> v;
22. For (int i = 0; i < ++i) {
24. V.push_back (i);
26. }
30. //Obtain a time-based seed:
32. Unsigned seed = Std::chrono::system_clock::now (). Time_since_epoch (). Count ();
34. Std::shuffle (V.begin (), V.end (), std::d efault_random_engine (Seed));
38. For (auto& it:v) {
40. Std::cout << It << "";
42. }
46. Std::cout << "\ n";
50. return 0;
52. }

Compile:

g++ main.cpp-o shuffle-std=c++0x

Execution output:

6 4 2 3 7 8 5 1 9

0

4 7 3 6 8 0 2 9 5

1

Std::shuffle-c++