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| #include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
#define ll long long
const int N = 1e6+10;
char str1[300],res[300];
int t,n,m,rk[N],s[N],tp[N],sa[N],tax[N],id[N],h[N];
bool vis[4444];
bool cmp(int *r,int a,int b,int l)
{
return r[a]==r[b]&&r[a+l]==r[b+l];
}
void da(int str[],int n,int m)
{
n++;
int i,j,p,*x=rk,*y=tp;
for(i=0;i<m;i++)tax[i]=0;
for(i=0;i<n;i++)tax[x[i]=str[i]]++;
for(i=1;i<m;i++)tax[i]+=tax[i-1];
for(i=n-1;i>=0;i--)sa[--tax[x[i]]]=i;
for(j=1;j<=n;j<<=1)
{
p=0;
for(i=n-j;i<n;i++)y[p++]=i;
for(i=0;i<n;i++)if(sa[i]>=j)y[p++]=sa[i]-j;
for(i=0;i<m;i++)tax[i]=0;
for(i=0;i<n;i++)tax[x[y[i]]]++;
for(i=1;i<m;i++)tax[i]+=tax[i-1];
for(i=n-1;i>=0;i--)sa[--tax[x[y[i]]]]=y[i];
swap(x,y);
p=1;x[sa[0]]=0;
for(i=1;i<n;i++)
x[sa[i]]=cmp(y,sa[i-1],sa[i],j)?p-1:p++;
if(p>=n)break;
m=p;
}
int k=0;
n--;
for(i=0;i<=n;i++)rk[sa[i]]=i;
for(i=0;i<n;i++)
{
if(k)k--;
j=sa[rk[i]-1];
while(str[i+k]==str[j+k])k++;
h[rk[i]]=k;
}
}
int check(int k){
int cnt = 0;
memset(vis,0,sizeof(vis));
for(int i=2;i<=n;i++){
if(h[i]<k){
memset(vis,0,sizeof(vis));
cnt=0;
continue;
}
if(!vis[id[sa[i-1]]])vis[id[sa[i-1]]]=1,cnt++;
if(!vis[id[sa[i]]])vis[id[sa[i]]]=1,cnt++;
if(cnt==t){
for(int j=0;j<k;j++)res[j]=s[sa[i]+j];
res[k]='\0';
return 1;
}
}
return 0;
}
int main(){
while(~scanf("%d",&t),t){
n=0;
int temp = 30;
for(int i=0;i<t;i++){
scanf("%s",str1);
int len = strlen(str1);
for(int j=0;j<len;j++){
s[n]=str1[j];
id[n++]=i;
}
s[n]='#'+i;
id[n++]='#'+i;
}
s[n]=0;
da(s,n,5000);
int ans = 0;
int l=1,r=strlen(str1);
while(l<=r){
int mid = (l+r)>>1;
if(check(mid)){
ans=1;
l=mid+1;
}
else r=mid-1;
}
if(!ans)printf("IDENTITY LOST\n");
else printf("%s\n",res);
}
return 0;
}
|