bzoj3976

题解：

先跑一下Sa

然后再用kmp匹配一下哪一些位置不行

然后二分答案

代码：

#include<bits/stdc++.h>
const int N=100003;
using namespace std;
int t[N],a[N],xx[N],yy[N],*x,*y,height[N],rank[N],sa[N];
int n,m,len,len1,pd[N],pd1[N],pd2[N],v[N],p,st[20][N],L[N];
char s1[N],s2[N],s3[N];
void get_fail()
{
    t[0]=-1; int j;
    for (int i=0;i<len1;i++)
     {
        j=t[i];
        while (j!=-1&&s3[j]!=s3[i]) j=t[j];
        t[i+1]=++j;
     }
}
void kmp(char s[N],int a[N],int l)
{
    int i=0; int j=0;
    while (j<=l)
     {
        if (s3[i]==s[j]||i==-1) i++,j++;
        else i=t[i];
        if (i==len1)
         {
            a[j-len1]=1;
            i=t[i];
         }
     }
}
int cmp(int i,int j,int k)
{
    return y[i]==y[j]&&(i+k>len?-1:y[i+k])==(j+k>len?-1:y[j+k]);
}
void get_sa()
{
    x=xx; y=yy; int m1=30;
    for (int i=1;i<=len;i++) v[x[i]=a[i]]++;
    for (int i=1;i<=m1;i++) v[i]+=v[i-1];
    for (int i=len;i>=1;i--) sa[v[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<=m1;i++) v[i]=0;
        for (int i=1;i<=len;i++) v[x[y[i]]]++;
        for (int i=1;i<=m1;i++) v[i]+=v[i-1];
        for (int i=len;i>=1;i--) sa[v[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;
        m1=p+1;
     }
    for (int i=1;i<=len;i++) rank[sa[i]]=i;
    p=0;
    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(0,p-1);
     }
}
int calc(int x,int y)
{
    int k=L[y-x]; 
    return max(st[k][x],st[k][y-(1<<k)+1]);
}
int divide(int l,int r)
{
    int t=l,ans=r+1;
    while (l<=r)
     {
        int mid=(l+r)/2;
        if (calc(t,mid)) ans=min(ans,mid),r=mid-1;
        else l=mid+1;
     } 
    return ans;
}
int main()
{
    scanf("%s",s1);
    n=strlen(s1);
    scanf("%s",s2);
    m=strlen(s2);
    scanf("%s",s3);
    len1=strlen(s3);
    get_fail();
    kmp(s1,pd1,n);
    kmp(s2,pd2,m);
    for (int i=1;i<=n;i++)a[i]=s1[i-1]-'a'+1,pd[i]=pd1[i-1];
    a[n+1]=0;len=n+1;
    for (int i=1;i<=m;i++)a[++len]=s2[i-1]-'a'+1,pd[len]=pd2[i-1];
    get_sa();
    for (int i=1;i<=len;i++)st[0][i]=pd[i];
    for (int i=1;i<=17;i++) 
     for (int j=1;j<=len;j++)
      if (j+(1<<i)-1<=len)st[i][j]=max(st[i-1][j],st[i-1][j+(1<<(i-1))]);
    int j=0;
    for (int i=1;i<=len;i++)
     {
        if (1<<(j+1)<=i) j++;
        L[i]=j;
     }
    int ans=0;
    for (int i=2;i<=len;i++)
     if (sa[i]<=n&&sa[i-1]>n+1||sa[i]>n+1&&sa[i-1]<=n)
      {
        int t=height[i];
        int pos=divide(sa[i],sa[i]+height[i]-len1);
        t=min(t,pos-sa[i]+1+len1-2);
        ans=max(ans,t);
      }
    printf("%d\n",ans);
}