HDU 1251 统计难题

HDU 1251 统计难题

Trie的简单应用。
在每个结点中，用sum_记录以这个结点及其祖先为前缀的单词数目，将单词插入trie时，顺带更新sum_。
以下是我的代码：

#include < iostream >
#include < string >
#include < cstdio >
using   namespace  std;

struct  TreeNode
{
    TreeNode()
    {
        sum_ = 0 ;
         for ( int  i = 0 ;i < 26 ;i ++ )
            son_[i] = NULL;
    }
    
     int  sum_;
    TreeNode  * son_[ 26 ];
};

class  Trie
{
     public :
        Trie()
        {
            father_ = new  TreeNode;
        }
         void  Insert( const   string   & s)
        {
            TreeNode  * p(father_);
             for ( int  i = 0 ;i < s.size();i ++ )
            {
                 if ( ! p -> son_[s[i] - ' a ' ])
                    p -> son_[s[i] - ' a ' ] = new  TreeNode;
                p = p -> son_[s[i] - ' a ' ];
                p -> sum_ ++ ;
            }
        }
         int  Query( const   string   & s)
        {
            TreeNode  * p(father_);
             for ( int  i = 0 ;i < s.size();i ++ )
            {
                p = p -> son_[s[i] - ' a ' ];
                 if ( ! p)
                     return   0 ;
            }
             return  p -> sum_;
        }
    
     private :
        TreeNode  * father_;
};

int  main()
{
     /*
    freopen("data.in","r",stdin);
    freopen("data.out","w",stdout);
    // */
    
     string  s;
    Trie trie;
     while (getline(cin,s)  &&   ! s.empty())
        trie.Insert(s);
     while (getline(cin,s)  &&   ! s.empty())
        cout << trie.Query(s) << endl;
    
return   0 ;
}