2017.3.4[hihocoder#1403]后缀数组一·重复旋律

好久没发博了。

后缀数组板子题。具体实现就不解释了，hihocoder很良心。

http://hihocoder.com/problemset/problem/1403

#include<cmath>
#include<queue>
#include<cstdio>
#include<vector>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define N 20010
#define RG register
#define inf 0x3f3f3f3f
#define Inf 99999999999999999LL
using namespace std;
typedef long long LL;
int h,k,n,t,ans,a[N],b[N],q[N],sa[N],ssa[N],cnta[N],cntb[N],heit[N],Rank[N],music[N];
inline int Abs(RG const int &a){return a>0?a:-a;}
inline int Max(RG const int &a,RG const int &b){return a>b?a:b;}
inline int Min(RG const int &a,RG const int &b){return a>b?b:a;}
inline int gi(){
    RG int x=0;RG bool flag=0;RG char c=getchar();
    while((c<'0'||c>'9')&&c!='-') c=getchar();
    if(c=='-') c=getchar(),flag=1;
    while(c>='0'&&c<='9') x=x*10+c-'0',c=getchar();
    return flag?-x:x;
}
inline void getsa(){
    for (int i=1;i<=n;++i)   ++cnta[music[i]];
    for (int i=1;i<=100;++i) cnta[i]+=cnta[i-1];
    for (int i=n;i;--i)      sa[cnta[music[i]]--]=i;
    Rank[sa[1]]=1;
    for (int i=2;i<=n;++i){
        Rank[sa[i]]=Rank[sa[i-1]];
        if(music[sa[i]]!=music[sa[i-1]])
            ++Rank[sa[i]];
    }
    for (int now=1;Rank[sa[n]]<n;now<<=1){
    memset(cnta,0,sizeof(cnta));
    memset(cntb,0,sizeof(cntb));
        for (int i=1;i<=n;++i){
            ++cnta[a[i]=Rank[i]];                 //rank即为上一次排序好的第一关键字
            ++cntb[b[i]=(i+now<=n)?Rank[i+now]:0];//rank[i+now]即为第二关键字
        }
        for (int i=1;i<=n;++i) cntb[i]+=cntb[i-1];
        for (int i=n;i;--i)    ssa[cntb[b[i]]--]=i;//ssa即为按第二关键字排的“假”sa
        for (int i=1;i<=n;++i) cnta[i]+=cnta[i-1];
        for (int i=n;i;--i)    sa[cnta[a[ssa[i]]]--]=ssa[i];//相当于把i替换为ssa[i]，从而达到双关键字排序的目的
        Rank[sa[1]]=1;
        for (int i=2;i<=n;++i){
            Rank[sa[i]]=Rank[sa[i-1]];
            if (a[sa[i]]!=a[sa[i-1]]||b[sa[i]]!=b[sa[i-1]]) ++Rank[sa[i]];
        }
    }
    for (int i=1,j=0;i<=n;++i){
        if(j) --j;
        while (music[i+j]==music[sa[Rank[i]-1]+j]) ++j;
        heit[Rank[i]]=j;
    }
}   
inline void work(){
    n=gi();k=gi();
    if(k==1){
    printf("%d
",n);
    return;
    }
    for (RG int i=1;i<=n;++i)
    music[i]=gi();
    getsa();
    //for (RG int i=1;i<=n;++i) cout<<heit[i]<<' ';
    //cout<<endl;
    for (RG int i=1;i<=n;++i){
    while(h<t&&heit[i]<heit[q[t]]) --t;
    q[++t]=i;
    //cout<<q[h+1]<<' '<<q[t]<<endl;
    while(q[h+1]<=q[t]-k+1) ++h;
    if(h<t) ans=Max(ans,heit[q[h+1]]);
    //cout<<ans<<endl;
    }
    printf("%d
",ans);
}
int main(){
    work();
    return 0;
}