二分搜索

int binarysort(int begin , int end , int target)
{
    if ( begin >end ) return -1 ;
    int middle = (begin + end ) >>1;
    if ( arr[middle ] == target ) return middle;
        else
            if ( target > arr[middle])
                binarysort( middle +1 , end, target);
            else 
                binarysort(begin , middle -1  , target);
                
}

int binarysort(int begin , int end , int target)
{
    int middle    ;
    while (  begin <= end )
    {
        middle = (begin + end)>>1;
        if ( arr[middle] == target)
            return middle;
        if ( target > arr[middle]) 
            begin = middle +1;
        else
            end = middle -1   ;
    }
    return -1;
}