POJ 3261 Milk Patterns <后缀数组+二分>

#include <iostream>
#include <algorithm>
using namespace std;

const int MAXN=20010;
struct node{
int x,id;
bool operator <(node& N){
if(x!=N.x) return x<N.x;
else return id<N.id;
}
}data[MAXN];
int sa[MAXN],height[MAXN],wm[MAXN],wa[MAXN],wb[MAXN],temp[MAXN];
int *rank,k;

bool cmp(int *r,int a,int b,int len){
return r[a]==r[b]&&r[a+len]==r[b+len];
}

void da(node *data,int n,int m){
int *x=wa,*y=wb,*t,p,i,j;
sort(data,data+n);
for(i=0;i<n;++i) sa[i]=data[i].id;
for(i=1,x[sa[0]]=0;i<n;++i) x[sa[i]]=(data[i].x==data[i-1].x)?m-1:m++;
for(j=1,p=1;p<n;j<<=1,m=p){
for(i=n-j,p=0;i<n;++i) y[p++]=i;
for(i=0;i<n;++i) if(sa[i]>=j) y[p++]=sa[i]-j;
for(i=0;i<m;++i) wm[i]=0;
for(i=0;i<n;++i) ++wm[x[y[i]]];
for(i=1;i<m;++i) wm[i]+=wm[i-1];
for(i=n-1;i>=0;--i) sa[--wm[x[y[i]]]]=y[i];
for(t=x,x=y,y=t,i=1,p=1,x[sa[0]]=0;i<n;++i) x[sa[i]]=cmp(y,sa[i],sa[i-1],j)?p-1:p++;
}
rank=x;
}

void getHeight(int *data,int n){
for(int i=0,k=0,j;i<n;height[rank[i++]]=k)
for(k?--k:k,j=sa[rank[i]-1];data[i+k]==data[j+k];++k);
}

bool judge(int x,int n){
int counter=1;
for(int i=1;i<=n;++i){
if(height[i]>=x) ++counter;
else counter=1;
if(counter==k) return true;
}
return false;
}

void solve(int n){
int l=0,r=n;
while(l<r){
int mid=l+(r-l+1)/2;
if(judge(mid,n)) l=mid;
else r=mid-1;
}
cout<<l<<endl;
}

int main(){
ios::sync_with_stdio(false);
int n;
cin>>n>>k;
for(int i=0;i<n;++i){
cin>>temp[i];
data[i].x=temp[i]+1;
data[i].id=i;
}
data
.x=0; data
.id=n;
da(data,n+1,1);
getHeight(temp,n);
solve(n);
return 0;
}