排序之-----快排

void re_fastsort( int a [], int left , int right ) {          if ( left > right )         {                 return ;         }          int begin = left ;          int end = right ;          int key = a [ left ];          while (begin < end)         {                 while (begin<end&& a [end]>key)                {                        end--;                }                 if (begin < end)                {                         a [begin]= a [end];                        begin++;                }                 while (begin < end&& a [begin] < key)                {                        begin++;                }                 if (begin < end)                {                         a [end] = a [begin];                        end--;                }         }          a [begin] = key;         re_fastsort( a , left , begin - 1);         re_fastsort( a , begin + 1, right ); }