| STL: random_shuffle |
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| Tuesday, 14 November 2006 | |
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C++ STL (Standard Template Library) is an ANSI/ISO standard that has become an integral part of C++ distributions. STL can be grouped into 6 components: containers, generic algorithms, iterators, function objects, adaptors, and allocators. Random_shuffle is one of the methods in generic algorithms component. To use this method, we must #include <algorithm> in the program. The method randomly put elements in a vector from [first, last). The method follows uniform distribution, i.e. the probability of each N element is 1/N [1]. The complexity of random_shuffle method is O(N) or linear. An example below shows how random_shuffle is used to randomly generate and assign data in a vector of size 10. #include <iostream.h> #include <algorithm> #include <vector> #define TOTAL 10 using namespace std; int main(char **argv, int argc){ vector<int> number(TOTAL); for(int i=0; i<TOTAL; i++) number[i] = i; for(int i=0; i<TOTAL; i++){ random_shuffle(number.begin(), number.end()); copy(number.begin(), number.end(), ostream_iterator<int> (cout, " ")); cout<<endl; } return EXIT_SUCCESS; } Output: 1 7 9 3 5 6 0 4 8 2 4 2 1 9 3 6 0 8 7 5 9 4 2 1 6 5 0 8 7 3 0 4 1 9 5 8 3 2 6 7 5 6 2 4 8 3 1 9 0 7 9 1 5 2 3 8 7 4 0 6 2 0 5 3 8 7 4 1 9 6 1 5 8 6 9 2 4 0 3 7 2 1 4 8 3 6 5 0 9 7 6 8 4 3 0 7 9 5 1 2 [1] Musser, D.R. Derge, G.J, and Saini, A., STL Tutorial and Reference Guide: C++ Programming with the Standard Template, 2nd edition, Addison Wesley, New Jersey, March 2001. |
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