random_shuffle

Random_shuffle:随机打乱容器.// TEMPLATE FUNCTION random_shuffletemplate<class _RanIt,class _Diff> inlinevoid _Random_shuffle(_RanIt _First, _RanIt _Last, _Diff *){// shuffle [_First, _Last)const int _RANDOM_BITS = 15;// minimum random bits from rand()const int _RANDOM_MAX = (1U << _RANDOM_BITS) - 1;_RanIt _Next = _First;for (unsigned long _Index = 2; ++_Next != _Last; ++_Index){// assume unsigned long big enough for _Diff countunsigned long _Rm = _RANDOM_MAX;unsigned long _Rn = _CSTD rand() & _RANDOM_MAX;for (; _Rm < _Index && _Rm != ~0UL;_Rm = _Rm << _RANDOM_BITS | _RANDOM_MAX)_Rn = _Rn << _RANDOM_BITS| (_CSTD rand() & _RANDOM_MAX);// build random value_STD iter_swap(_Next, _First + _Diff(_Rn % _Index));// swap a pair}}函数产生一个随机容器.// TEMPLATE FUNCTION random_shuffle WITH RANDOM FNtemplate<class _RanIt,class _Fn1,class _Diff> inlinevoid _Random_shuffle(_RanIt _First, _RanIt _Last, _Fn1& _Func, _Diff *){// shuffle nonempty [_First, _Last) using random function _Func_RanIt _Next = _First;for (_Diff _Index = 2; ++_Next != _Last; ++_Index)_STD iter_swap(_Next, _First + _Diff(_Func(_Index) % _Index));}这个函数就比较容易理解.举例:class MyRadom{public:ptrdiff_t operator()( ptrdiff_t max ){double temp;temp = static_cast<double>( rand() )/ static_cast<double>(RAND_MAX);return static_cast<ptrdiff_t>(temp*max );}};int main(){vector<int> vecInt;for ( int i = 0;i <= 9;++ i ){vecInt.push_back( i );}random_shuffle( vecInt.begin(),vecInt.end() );random_shuffle( vecInt.begin(),vecInt.end(),MyRadom() );copy( vecInt.begin(),vecInt.end(),ostream_iterator<int>( cout," " ) );system( "pause" );return 0;}