bzoj 1014 [JSOI2008]火星人prefix (splay+二分答案+字符串hash)

  1 #include <cstdio>
  2 #include <cstring>
  3 #include <algorithm>
  4 #define il inline
  5 #define ui unsigned int  
  6 #define ull unsigned long long 
  7 #define seed 13131
  8 #define N 110000
  9 #define root d[0].ch[1]
 10 using namespace std;
 11 
 12 char str[N],Q[10],q[10];
 13 ull pw[N];
 14 int n,m,tot;
 15 struct SPLAY{int fa,ch[2],sz;ull hsh,val;}d[N];
 16 int gc()
 17 {
 18     int rett=0,fh=1;char p=getchar();
 19     while(p<‘0‘||p>‘9‘){if(p==‘-‘)fh=-1;p=getchar();}
 20     while(p>=‘0‘&&p<=‘9‘){rett=(rett<<3)+(rett<<1)+p-‘0‘;p=getchar();}
 21     return rett*fh;
 22 }
 23 il ull idx(char c){return c-‘a‘+1;}
 24 il void con(int x,int ff,int p){d[x].fa=ff,d[ff].ch[p]=x;}
 25 il int idf(int x){return d[d[x].fa].ch[0]==x?0:1;}
 26 il int cre(ull w){tot++;d[tot].val=w,d[tot].sz=1,d[tot].hsh=w;return tot;}
 27 il void pushup(int x)
 28 {
 29     d[x].sz=d[d[x].ch[0]].sz+d[d[x].ch[1]].sz+1;
 30     d[x].hsh=d[d[x].ch[0]].hsh*pw[d[d[x].ch[1]].sz+1]+(ull)d[x].val*pw[d[d[x].ch[1]].sz]+d[d[x].ch[1]].hsh;
 31 }
 32 il void rot(int x)
 33 {
 34     int y=d[x].fa;int ff=d[y].fa;int px=idf(x);int py=idf(y);
 35     con(d[x].ch[px^1],y,px),con(y,x,px^1),con(x,ff,py);
 36     pushup(y),pushup(x);
 37 }
 38 void splay(int x,int to)
 39 {
 40     to=d[to].fa;
 41     while(d[x].fa!=to){
 42         int y=d[x].fa;
 43         if(d[y].fa==to) rot(x);
 44         else if(idf(x)==idf(y)){rot(y);rot(x);}
 45         else{rot(x);rot(x);}
 46     }
 47 }
 48 int build(int l,int r,int ff)
 49 {
 50     if(l>r) return 0;
 51     int mid=(l+r)>>1;
 52     int pos=cre(idx(str[mid]));
 53     d[pos].fa=ff;
 54     d[pos].ch[0]=build(l,mid-1,pos);
 55     d[pos].ch[1]=build(mid+1,r,pos);
 56     pushup(pos);
 57     return pos;
 58 }
 59 int find_pos(int pos)
 60 {
 61     int x=root;
 62     while(x)
 63     {
 64         if(d[d[x].ch[0]].sz>=pos) x=d[x].ch[0];
 65         else{
 66             pos-=d[d[x].ch[0]].sz;
 67             if(pos==1) return x;
 68             pos--,x=d[x].ch[1];
 69         }
 70     }
 71     return x;
 72 }
 73 void ins(int pos,ull w)
 74 {
 75     int ff=find_pos(pos+1),x,y;splay(ff,root);
 76     if(!d[ff].ch[1]) 
 77         x=cre(w),con(x,ff,1),pushup(ff);
 78     else{
 79         x=d[ff].ch[1];
 80         while(x)
 81             if(d[x].ch[0]) x=d[x].ch[0];
 82             else break;
 83         y=cre(w),con(y,x,0),pushup(x);
 84         splay(x,root);
 85     }
 86 }
 87 void replac(int pos,ull w)
 88 {
 89     int x=find_pos(pos+1);splay(x,root);
 90     d[x].val=w;pushup(x);
 91 }
 92 il ull get_hsh(int pos)
 93 {
 94     int x=find_pos(pos);
 95     splay(x,root);
 96     int y=find_pos(n+2);
 97     splay(y,d[x].ch[1]);
 98     return d[d[d[x].ch[1]].ch[0]].hsh;
 99 }
100 il int check(int x,int y,int mid)
101 {
102     ull s1=0,s2=0,s3=0,s4=0;
103     s1=get_hsh(x);
104     if(x+mid<=n) s2=get_hsh(x+mid);
105     s3=get_hsh(y);
106     if(y+mid<=n) s4=get_hsh(y+mid);
107     return (s1-s2==(s3-s4)*pw[y-x])?1:0;
108 }
109 int Query(int a,int b)
110 {
111     if(a>b){int t=a;a=b;b=t;}
112     int l=1,r=n-b+1,ans=0;
113     while(l<=r){
114         int mid=(l+r)>>1;
115         if(check(a,b,mid)) ans=mid,l=mid+1;
116         else r=mid-1;
117     }
118     return ans;
119 }
120 void stt()
121 {
122     n=strlen(str+1);pw[0]=1;
123     for(int i=1;i<=100000;i++) pw[i]=pw[i-1]*seed;
124     int x=cre(0),y=cre(0),z;
125     con(x,0,1),con(y,1,1);
126     z=build(1,n,y);
127     con(z,y,0);
128     pushup(y),pushup(x);
129 }
130 
131 int main()
132 {
133     scanf("%s",str+1);
134     stt();
135     scanf("%d",&m);
136     int x,y;
137     for(int i=1;i<=m;i++)
138     {
139         scanf("%s",Q);
140         if(Q[0]==‘Q‘){
141             x=gc(),y=gc();
142             printf("%d\n",Query(x,y));
143         }else if(Q[0]==‘I‘){
144             x=gc();scanf("%s",q);
145             ins(x,idx(q[0]));
146             n++;
147         }else{
148             x=gc();scanf("%s",q);
149             replac(x,idx(q[0]));
150         }
151     }
152     return 0;
153 }