[Hash] BZOJ 4236 JOIOJI

来源：互联网发布：对亚投行的看法知乎编辑：程序博客网时间：2024/04/29 23:13

把 (y-x，z-x）hash 一下就好了

#include<cstdio>#include<cstdlib>#include<algorithm>using namespace std;inline char nc(){static char buf[100000],*p1=buf,*p2=buf;if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }return *p1++;}inline void read(int &x){char c=nc(),b=1;for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1;for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b;}inline void read(char *s){char c=nc(); int len=0;for (;!(c=='J' || c=='O' || c=='I');c=nc());for (;c=='J' || c=='I' || c=='O';s[++len]=c,c=nc()); s[++len]=0;}const int N=200005;namespace hashmap{const int M=5000;struct node{int x,y,pos;int next;}G[N];int head[M][M],inum;int Solve(int x,int y,int pos){int sx=(x%M+M)%M,sy=(y%M+M)%M;for (int p=head[sx][sy];p;p=G[p].next)if (G[p].x==x && G[p].y==y)return pos-G[p].pos;G[++inum].x=x; G[inum].y=y; G[inum].pos=pos; G[inum].next=head[sx][sy]; head[sx][sy]=inum;return -1;}}int n;char str[N];int main(){using namespace hashmap;int x=0,y=0,ans=0;freopen("t.in","r",stdin);freopen("t.out","w",stdout);read(n);read(str);Solve(0,0,0);for (int i=1;i<=n;i++){if (str[i]=='J') x--,y--;if (str[i]=='O') x++;if (str[i]=='I') y++;ans=max(ans,Solve(x,y,i));}printf("%d\n",ans);return 0;}

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