hdu 1800 Flying to the Mars

http://acm.hdu.edu.cn/showproblem.php?pid=1800

/**/ /*
5
1001
0010
0110
2
4
*/
#include < iostream >
using   namespace  std;
int  i;
struct  dictree 
{
    struct dictree *child[10];
    int num;
    dictree()
    {
        for(i=0;i<10;i++)
            child[i]=NULL;
        num = 0;
    }
    ~dictree()
    {
        for(i=0;i<10;i++)
            if(child[i])
                delete child[i];
    }
} ;
int  main()
{
    int n;
    while(cin>>n)
    {
        int maxs = 0;
        char digit[31];
        struct dictree root;
        while(n--)
        {
            cin>>digit;
            char *tmp = digit;
            while(*tmp == '0')//去掉前缀0
                tmp++;
            struct dictree *now = &root;
            while(*tmp>='0' && *tmp<='9')//注意不能写成*tmp
            {
                if(now->child[*tmp-'0'] == NULL)
                    now->child[*tmp-'0'] = new dictree;
                now = now->child[*tmp-'0'];
                //now->num++;//不能再加
                tmp++;
            }
            now->num++;            
            if( maxs < now->num)
                maxs = now->num;
        }
        cout<<maxs<<endl;
    }
    return 0;
}