hdu1867 A + B for you again KMP

#include<iostream>
#include<cstdio>
#include<cstring>

using namespace std;
const int N=100005;
int next
;

void init(char *s)//get next[]
{
int i,j;
next[0]=0;
for(i=1,j=0;s[i];i++)
{
while(j>0&&s[j]!=s[i])
j=next[j-1];
if(s[j]==s[i])
j++;
next[i]=j;
}
}

int getLength(char *s1,char *s2)//get the length of the same part
{
int i,j;
init(s2);
for(i=j=0;;i++)
{
while(j>0&&s1[i]!=s2[j])
j=next[j-1];
if(s1[i]==s2[j])
j++;
if(s1[i+1]=='\0')
break;
if(s2[j]=='\0')
j=0;
}
return j;
}

void output(char *s1,char *s2,int n)
{
int len=strlen(s1);
for(int i=0;i<len-n;i++)
putchar(s1[i]);
printf("%s\n",s2);
}

int main()
{
char s1
,s2
;
while(~scanf("%s%s",s1,s2))
{
int len1=getLength(s1,s2);
int len2=getLength(s2,s1);
if(len1>len2)
output(s1,s2,len1);
else if(len2>len1)
output(s2,s1,len2);
else
{
if(strcmp(s1,s2)<0)
output(s1,s2,len1);
else
output(s2,s1,len2);
}
}
return 0;
}