Manacher

HDU 3068 Manacher裸题

 #include <cstdio>
 #include <cstring>
 const int Maxn=;
 char Str[Maxn<<],STR[Maxn<<];
 int Len,x,P[Maxn<<],Id,Mx;
 inline int Max(int x,int y) {return x>y?x:y;}
 inline int Min(int x,int y) {return x>y?y:x;}
 inline Init()
 {
     Len=strlen(Str+);
     for (int i=;i<=Len;i++) STR[i]=Str[i];
     Str[]='$'; Str[]='#';
     for (int i=;i<=Len;i++) Str[i<<]=STR[i],Str[i<<|]='#';
     Len=Len<<|; Id=;Mx=;
 }
 inline int Manacher()
 {
     for (int i=;i<=Len;i++)
     {
         if (Mx>i) P[i]=Min(P[*Id-i],Mx-i); else P[i]=;
         while (Str[i+P[i]]==Str[i-P[i]]) P[i]++;
         if (i+P[i]>Mx) Mx=P[i]+i,Id=i;
     }
     int Ret=;
     for (int i=;i<=Len;i++)  Ret=Max(Ret,P[i]);
     return Ret-;
 }
 int main()
 {
     while (scanf("%s",Str+)!=EOF)
     {
         Init();
         printf("%d\n",Manacher());
     }
     return ;
 }

C++

BZOJ 3790 线段求交

用Manacher把最大的回文半径求出然后线段求交即可

 #include <iostream>
 #include <cstring>
 #include <cstdio>
 #include <algorithm>
 #include <vector>
 #define mp make_pair
 #define pb push_back
 #define PA pair<int,int>
 #define fi first
 #define se second
 using namespace std;
 const int Maxn=;
 const int Inf=0x3f3f3f3f;
 char S[Maxn],Str[Maxn];
 int P[Maxn],c[Maxn];
 int Len;
 vector<PA> Line;
 inline int Min(int x,int y) {return x>y?y:x;}
 inline int lowbit(int x) {return x&-x;}
 inline int Query(int x)
 {
     if (x==) return ;
     int Ret=Inf;
     for (int i=x;i<=Len;i+=lowbit(i))    Ret=Min(Ret,c[i]);
     return Ret;
 }
 inline void Update(int x,int y)
 {
     for (int i=x;i;i-=lowbit(i)) c[i]=Min(c[i],y);
 }
 inline void Manacher()
 {
     int m=Len<<|;
     for (int i=;i<=Len;i++)
     {
         S[i<<]=Str[i];
         S[i<<|]='#';
     }
     S[]='#'; S[]='&'; S[m+]='^';
     int Mx=,Id=;
     for (int i=;i<=m;i++)
     {
         if (i<Mx) P[i]=Min(Mx-i,P[*Id-i]); else P[i]=;
         while (S[i-P[i]]==S[i+P[i]]) P[i]++;
         if (i+P[i]>Mx) Mx=i+P[i],Id=i;
         int l=(i-P[i])/+,r=(i+P[i])/-;
         if (l<=r) Line.pb(mp(r,l));
     }
 }
 int main()
 {
     while (scanf("%s",Str+)!=EOF)
     {
         Len=strlen(Str+); Line.clear();
         Manacher();
         sort(Line.begin(),Line.end());
         for (int i=;i<=Len;i++) c[i]=Inf;
         int Ans=Inf;
         for (int i=;i<Line.size();i++)
         {
             int x=Query(Line[i].se-)+;
             Update(Line[i].fi,x);
             if (Line[i].fi==Len) Ans=Min(Ans,x);
         }
         printf("%d\n",Ans-);
     }
     return ;
 }

C++