HDU-1800-Flying to the Mars

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int Max;
struct node
{
int count;
node *childs[10];
node()
{
count=0;
int i;
for(i=0;i<=9;i++)
childs[i]=NULL;
}
};
node *root,*current,*newnode;
void insert(char *str)
{
int i,m;
current=root;
for(i=0;i<strlen(str);i++)
{
m=str[i]-'0';
if(current->childs[m]!=NULL)
current=current->childs[m];
else
{
newnode=new node;
current->childs[m]=newnode;
current=newnode;
}
}
++(current->count);
if((current->count)>Max)
Max=(current->count);
}
int main()
{
int n,i,len;
char s[40],str[40];
while(scanf("%d",&n)!=EOF)
{
Max=-1;
root=new node;
while(n--)
{
scanf("%s",s);
len=strlen(s);
for(i=0;i<len-1;i++)
if(s[i]!='0')
break;
if(i==len-1)
{
str[0]=s[len-1];
str[1]='\0';
}
else
{
strncpy(str,&s[i],len-i);
str[len-i]='\0';
}
insert(str);
}
printf("%d\n",Max);
}
return 0;
}