SRM 444

SRM 444

又在第一题上花了很多时间，这次更夸张。。用了20多分钟。。。最后提交时只有150分了。。
第二题，一看挺简单，就是求质因数的个数，然后看能被4的几次幂整除。
一开始匆忙写了一个，然后提交，400分。
代码如下：

               int  getLevel( long   long  N) 
                  { 
                  
                   int  res  =   0 ;
                                  
                   for ( long   long  i = 2 ;i * i <= N; ++ i){                          
                            while (N % i == 0 ){
                                         res ++ ;
                                         N /= i;
                                         }                                                                          
                           }
                                                            
                   int  r = 0 ;
                   while (res / 4 != 0 ){
                                  res /= 4 ;
                                  r ++ ;
                   }

                  return  r;
                  } 

后来一看，i*i<=N这时，N一直在变，应该保存下N或者直接求sqrt(N)。一开始不太确定sqrt能否处理long long，因此用相乘的方法。后来cha人的时候，发现一个也犯了同样的错误，马上构造56=2*2*2*7,cha掉
于是改成下面，提交，只有299分了。。。

               int  getLevel( long   long  N) 
                  { 
                  
                   int  res  =   0 ;
                   long   long  T  =  N;  // 增加这一行            
                   for ( long   long  i = 2 ;i * i <= T; ++ i){                          
                            while (N % i == 0 ){
                                         res ++ ;
                                         N /= i;
                                         }                                                                          
                   }
                                                            
                   int  r = 0 ;
                   while (res / 4 != 0 ){
                                  res /= 4 ;
                                  r ++ ;
                   }

                   return  r;
                  } 

结果还是被cha掉了。因为犯了一个严重的错误，没有算上最后一个质因数，这个质因数可能大于sqrt(N)。如88==2*2*2*11。
正确代码应该是

               int  getLevel( long   long  N) 
                  { 
                  
                   int  res  =   0 ;
                   long   long  T  =  N;          
                   for ( long   long  i = 2 ;i * i <= T; ++ i){                          
                            while (N % i == 0 ){
                                         res ++ ;
                                         N /= i;
                                         }                                                                          
                   }
                          
                    if (N != 1 ) res ++ ;  // 增加这一行
                                 
                   int  r = 0 ;
                   while (res / 4 != 0 ){
                                  res /= 4 ;
                                  r ++ ;
                   }

                   return  r;
                  } 

最后房间只有一人过了第二题。
还好cha了4个，不然rating要跌不少了。。
还好rating还是涨了一点点。。
太粗心了，不然就应该能进div1了。。