BZOJ 1014 [JSOI2008]火星人prefix | Splay维护哈希值

题目:

 

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题解:

#include<cstdio>
#include<algorithm>
#include<cstring>
typedef long long ll;
#define N 100010
#define Base 29
#define which(x) (ls[fa[(x)]]==(x))
using namespace std;
int n,m,idx,root,fa[N],ls[N],rs[N],val[N],sz[N],a,b;
ll hsh[N],pw[N];
char s[N],op[10];
void upt(int u)
{
    sz[u]=sz[ls[u]]+sz[rs[u]]+1;
    hsh[u]=hsh[ls[u]]+val[u]*pw[sz[ls[u]]]+hsh[rs[u]]*pw[sz[ls[u]]+1];
}
void rotate(int u)
{
    int v=fa[u],w=fa[v],b=which(u)?rs[u]:ls[u];
    if (w) which(v)?ls[w]=u:rs[w]=u;
    which(u)?(ls[v]=b,rs[u]=v):(rs[v]=b,ls[u]=v);
    fa[u]=w,fa[v]=u;
    if (b) fa[b]=v;
    upt(v),upt(u);
}
void splay(int u,int tar)
{
    while (fa[u]!=tar)
    {
    if (fa[fa[u]]!=tar)
        (which(u)==which(fa[u]))?rotate(fa[u]):rotate(u);
    rotate(u);
    }
    if (!tar) root=u;
}
int build(int l,int r,int pre)
{
    if (l>r) return 0;
    int u=++idx,mid=l+r>>1;
    val[u]=s[mid]-'a'+1,fa[u]=pre;
    ls[u]=build(l,mid-1,u);
    rs[u]=build(mid+1,r,u);
    upt(u);
    return u;
}
int find(int x)
{
    int u=root;
    while(sz[ls[u]]!=x)
    if (x<=sz[ls[u]]-1) u=ls[u];
    else x-=sz[ls[u]]+1,u=rs[u];
    return u;
}
void insert(int pos,int x)
{
    int u=find(pos),v=find(pos+1);
    splay(u,0),splay(v,u);
    ls[v]=++idx,fa[idx]=v,val[idx]=x,sz[idx]=1;
    splay(idx,0);
}
void change(int pos,int x)
{
    int u=find(pos);
    val[u]=x;
    splay(u,0);
}
ll gethsh(int pos,int len)
{
    int u=find(pos-1),v=find(pos+len);
    splay(u,0),splay(v,u);
    return hsh[ls[v]];
}
int query(int a,int b)
{
    int l=0,r=sz[root]-max(a,b)-1,mid;
    while (l<r)
    {
    mid=l+r+1>>1;
    if (gethsh(a,mid)==gethsh(b,mid)) l=mid;
    else r=mid-1;
    }
    return l;
}
int main()
{
    scanf("%s",s+1);
    n=strlen(s+1);
    pw[0]=1;
    for (int i=1;i<N;i++)
    pw[i]=pw[i-1]*Base;
    root=build(0,n+1,0);
    scanf("%d",&m);
    while (m--)
    {
    scanf("%s",op);
    if (op[0]=='Q')
    {
        scanf("%d%d",&a,&b);
        printf("%d\n",query(a,b));
    }
    else if (op[0]=='I')
    {
        int pos;
        scanf("%d%s",&pos,op);
        insert(pos,op[0]-'a'+1);
    }
    else if (op[0]=='R')
    {
        int pos;
        scanf("%d%s",&pos,op);
        change(pos,op[0]-'a'+1);
    }
    }
    return 0;
}