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random_shuffle
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思路：
必须是 RandomAccessIterator
1.遍历区间
2.产生[0,i)中的一个随机数rand。将*(first+rand)与i交换
??怎么证明随机性
源代码：
template <class RandomAccessIterator>
inline void random_shuffle(RandomAccessIterator first,
RandomAccessIterator last) {
__random_shuffle(first, last, distance_type(first));
}
template <class RandomAccessIterator, class RandomNumberGenerator>
void random_shuffle(RandomAccessIterator first, RandomAccessIterator last,
RandomNumberGenerator& rand) { //这里必须是传引用。
由于随机数产生器有局部状态。每次被调用都会改变 if (first == last) return; for (RandomAccessIterator i = first + 1; i != last; ++i) iter_swap(i, first + rand((i - first) + 1)); } template <class RandomAccessIterator, class Distance> 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 }
演示样例：
int main()
{
vector<int> 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<int>(cout, " "));
}
本文转自mfrbuaa博客园博客，原文链接：http://www.cnblogs.com/mfrbuaa/p/5217449.html，如需转载请自行联系原作者
