poj 3294 Life Forms （后缀数组）

3
abcdefg
bcdefgh
cdefghi
3
xxx
yyy
zzz
0

bcdefg
cdefgh

?

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#define N 200003
using namespace std;
int sa
,rank
,height
,xx
,yy
,*x,*y;
int n,m,len,p,vis
,cnt,q
,b
,a
,ans,pos
;
char s
;
void init()
{
memset(sa,0,sizeof(sa));
memset(rank,0,sizeof(rank));
memset(height,0,sizeof(height));
memset(b,0,sizeof(b));
memset(q,0,sizeof(q));
memset(vis,0,sizeof(vis));
}
int cmp(int i,int j,int l)
{
return y[i]==y[j]&&(i+l>len?-1:y[i+l])==(j+l>len?-1:y[j+l]);
}
void get_SA()
{
x=xx; y=yy; m=200;
for (int i=1;i<=len;i++) b[x[i]=a[i]]++;
for (int i=1;i<=m;i++) b[i]+=b[i-1];
for (int i=len;i>=1;i--) sa[b[x[i]]--]=i;
for (int k=1;k<=len;k<<=1) {
p=0;
for (int i=len-k+1;i<=len;i++) y[++p]=i;
for (int i=1;i<=len;i++)
if (sa[i]>k) y[++p]=sa[i]-k;
for (int i=1;i<=m;i++) b[i]=0;
for (int i=1;i<=len;i++) b[x[y[i]]]++;
for (int i=1;i<=m;i++) b[i]+=b[i-1];
for (int i=len;i>=1;i--) sa[b[x[y[i]]]--]=y[i];
swap(x,y); p=2; x[sa[1]]=1;
for (int i=2;i<=len;i++)
x[sa[i]]=cmp(sa[i],sa[i-1],k)?p-1:p++;
if (p>len) break;
m=p+1;
}
p=0;
for (int i=1;i<=len;i++) rank[sa[i]]=i;
for (int i=1;i<=len;i++) {
if (rank[i]==1) continue;
int j=sa[rank[i]-1];
while (i+p<=len&&j+p<=len&&a[i+p]==a[j+p]) p++;
height[rank[i]]=p;
p=max(p-1,0);
}
}
int pd(int x)
{
memset(vis,0,sizeof(vis));
int size=1; vis[pos[sa[1]]]=1;
int last=0;
for (int i=2;i<=len;i++)
if (height[i]>=x)
{
int t=pos[sa[i]];
if (!vis[t])
vis[t]++,size++;
}
else {
if (size>=n/2+1) return 1;
for (int j=last;j<=i-1;j++)
vis[pos[sa[j]]]=0;
size=1; last=i; vis[pos[sa[i]]]=1;
}
if (size>=n/2+1) return 1;
return 0;
}
void solve()
{
memset(vis,0,sizeof(vis));
int size=1; int last=0; vis[pos[sa[1]]]=1;
for (int i=2;i<=len;i++)
if (height[i]>=ans) {
int t=pos[sa[i]];
if (!vis[t])
vis[t]++,size++;
}
else {
if (size>=n/2+1) q[++cnt]=sa[i-1];
for (int j=last;j<=i-1;j++)
vis[pos[sa[j]]]=0;
size=1; last=i; vis[pos[sa[i]]]=1;
}
if (size>=n/2+1) q[++cnt]=sa
;
}
int main()
{
freopen("a.in","r",stdin);
freopen("my.out","w",stdout);
while(true) {
init();
scanf("%d",&n);
if (!n) break; len=0;
for (int i=1;i<=n;i++) {
scanf("%s",s+1);
m=strlen(s+1);
if (i!=1) a[++len]=i+27;
for (int j=1;j<=m;j++)
a[++len]=s[j]-'a'+1,pos[len]=i;
}
get_SA();
int l=1; int r=len; ans=0;
while (l<=r) {
int mid=(l+r)/2;
if (pd(mid)) ans=max(ans,mid),l=mid+1;
else r=mid-1;
}
cnt=0;
solve(); bool pd=false;
if (!ans) printf("?\n");
else {
for (int i=1;i<=cnt;i++){
if (pos[q[i]]==pos[q[i]+ans-1])
{
pd=true;
for (int j=q[i];j<=q[i]+ans-1;j++)
printf("%c",a[j]+'a'-1);
printf("\n");
}
}
if (!pd) printf("?\n");
}
printf("\n");
}
}