cf873-Forbidden-Indices- Suffix Array - disjoint-set

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Given a string s, and certain legal provisions of some of the characters are not legitimate.

begging $|a|*f(a)$ maximum, $a$ sub s string, $f(a)$ for the emergence of a legitimate end to the number of characters.

analysis

Built suffix array, according to an array of descending height merger, disjoint-set maintenance.

Since the child can not be calculated at the end of the string, including illegal, and suffix arrays can not easily determine whether the end of the substring legitimate, so we flipped first string s, this problem will be transformed into the beginning of the substring is legitimate.

When we initialize disjoint-set, beginning with the suffix legal character size is set to 1, the beginning of the illegal character suffix is ​​set to 0. After the height sort an array, then descending the merger, each update answer.

In addition only appear once substring require special sentence.

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
#define debug(x) cerr<<#x<<' '<<x<<'\n'
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,a,b) for(int i=(a);i>=(b);i--)
const int maxn=2e5+10;
const int mod=1e9+7;
const int inf=0x3f3f3f3f;
const int maxbit=20;
struct SuffixArray
{
    int sa[maxn], rank[maxn], ws[maxn], wv[maxn], wa[maxn], wb[maxn], height[maxn], st[maxbit][maxn], N;
    bool cmp(int *r, int a, int b, int l){return r[a]==r[b] and r[a+l]==r[b+l];}
    void build(int *r, int n, int m)
    {
        N=n;
        n++;
        int i, j, k=0, p, *x=wa, *y=wb, *t;
        for(i=0;i<m;i++)ws[i]=0;
        for(i=0;i<n;i++)ws[x[i]=r[i]]++;
        for(i=1;i<m;i++)ws[i]+=ws[i-1];
        for(i=n-1;i>=0;i--)sa[--ws[x[i]]]=i;
        for(p=j=1;p<n;j<<=1,m=p)
        {
            for(p=0,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<n;i++)wv[i]=x[y[i]];
            for(i=0;i<m;i++)ws[i]=0;
            for(i=0;i<n;i++)ws[wv[i]]++;
            for(i=1;i<m;i++)ws[i]+=ws[i-1];
            for(i=n-1;i>=0;i--)sa[--ws[wv[i]]]=y[i];
            for(t=x,x=y,y=t,p=1,i=1,x[sa[0]]=0;i<n;i++)
                x[sa[i]]=cmp(y,sa[i-1],sa[i],j)?p-1:p++;
        }

        for(i=0;i<n;i++)rank[sa[i]]=i;

        for(i=0;i<n-1;height[rank[i++]]=k)
            for(k?k--:0,j=sa[rank[i]-1];r[i+k]==r[j+k];k++);
    }
    void build_st()     //st表
    {
        int i, k;
        for(i=1;i<=N;i++)st[0][i]=height[i];
        for(k=1;k<=maxbit;k++)
            for(i=1;i+(1<<k)-1<=N;i++)
                st[k][i]=min(st[k-1][i],st[k-1][i+(1<<k)-1]);
    }
    int lcp(int x, int y)   //最长公共前缀
    {
        int l=rank[x], r=rank[y];
        if(l>r)swap(l,r);
        if(l==r)return N-sa[l];
        int t=log2(r-l);
        return min(st[t][l+1],st[t][r-(1<<t)+1]);
    }
}SA;
int strcp[maxn],fa[maxn];
ll siz[maxn];
bool can[maxn];
pii pos[maxn];
int Find(int x) {
    if(x==fa[x]) return x;
    else return fa[x]=Find(fa[x]);
}
void Union(int a,int b) {
    int faa=Find(a),fab=Find(b);
    siz[faa]+=siz[fab];
    fa[fab]=faa;
}
int main()
{
    ios::sync_with_stdio(false);cin.tie(0);
    int len;
    cin>>len;
    string a,b;
    cin>>a;
    cin>>b;
    rep(i,0,len-1) {
        strcp[len-i-1]=a[i];
        if(b[i]=='0') can[len-i-1]=true;
        else can[len-i-1]=false;
    } 
    ll ans=0;
    rep(i,0,len) {
        fa[i]=i;
        if(can[i]) {
            siz[i]=1;
            ans=max(ans,(ll)len-i);
        } 
    }
    strcp[len]=0;
    SA.build(strcp,len,300);
    int num=0;
    rep(i,2,len) {
        pos[num].fi=SA.height[i];
        pos[num++].se=i;
    }
    sort(pos,pos+num);
    per(i,num-1,0) {
        int l=SA.sa[pos[i].se-1],r=SA.sa[pos[i].se];
        l=Find(l),r=Find(r);
        ans=max(ans,(siz[l]+siz[r])*pos[i].fi);
        Union(l,r);
    }
    cout<<ans<<'\n';
    return 0;
}