POJ3261 Milk Patterns，后缀数组, 出现k次的重复子串

也是根据height来计算前缀，同时利用二分来检索答案，根据每次二分的最少长度来给height来分组

/******************************************************************************* # Author : Neo Fung # Email : [e-mail] # Last modified: 2012-06-02 22:02 # Filename: POJ3261 Milk Patterns.cpp # Description : 后缀数组, 出现k次的重复子串 ******************************************************************************/#ifdef _MSC_VER#define DEBUG#define _CRT_SECURE_NO_DEPRECATE#endif#include <fstream>#include <stdio.h>#include <iostream>#include <string.h>#include <string>#include <limits.h>#include <algorithm>#include <math.h>#include <numeric>#include <functional>#include <ctype.h>using namespace std;const int kMAXN=20010;int w[50*kMAXN],wa[kMAXN],wb[kMAXN],wv[kMAXN],array[kMAXN],sa[kMAXN];// int cmp(const int *r,const int &a,const int &b,const int &l){  return r[a]==r[b]&&r[a+l]==r[b+l];}// 倍增算法// r为待比较数组；n为r的长度；m为r中元素的最大值 void DoublingAlgorithm(const int *r,int *sa,const int &n,int m){  int i,j,p,*x=wa,*y=wb,*t;  for (i=0;i<m;i++) w[i]=0;  for (i=0;i<n;i++) w[x[i]=r[i]]++;  for (i=1;i<m;i++) w[i]+=w[i-1];  for (i=n-1;i>=0;i--) sa[--w[x[i]]]=i;  for (p=1,j=1;p<n;j*=2,m=p){    for (p=0,i=n-j;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++) w[i]=0;    for (i=0;i<n;i++) w[wv[i]=x[y[i]]]++;    for (i=1;i<m;i++) w[i]+=w[i-1];    for (i=n-1;i>=0;i--) sa[--w[wv[i]]]=y[i];    for (t=x,x=y,y=t,p=1,i=1,x[sa[0]]=0;i<n;i++)      x[sa[i]]=cmp(y,sa[i-1],sa[i],j)?p-1:p++;  }  return;}// 计算height数组，r和sa的定义同上；// height的下标从1开始，到n结束，包含n；int rank[kMAXN],height[kMAXN];void CalculateHeight(const int *r,int *sa,const int &n){  int i,j,k=0;  for (i=1;i<=n;i++) rank[sa[i]]=i;  for (i=0;i<n;height[rank[i++]]=k)    for (k?k--:0,j=sa[rank[i]-1];r[i+k]==r[j+k];k++);  return;}// k为最小公共前缀长度bool Check(const int &k,const int &repeat,const int &n){int cnt;for(int i=1;i<=n;++i){if(height[i]<k){cnt=1;}else{if(++cnt>=repeat)return true;}}return false;}// 二分检索，l是左起点坐标，r是右起点坐标（包含r）int BinSearch(int l,int r,const int &repeat,const int &n){while(l+1<r){int mid=(l+r)>>1;if (Check(mid,repeat,n)) l=mid; else r=mid;}return l;}int main(void){#ifdef DEBUG  freopen("../stdin.txt","r",stdin);freopen("../stdout.txt","w",stdout); #endif  int n,m,ncase=1;while(~scanf("%d%d",&n,&m) && n){int end=0; for(int i=0;i<n;++i){scanf("%d",&array[i]);end=max(array[i],end);}array[n]=0;DoublingAlgorithm(array,sa,n+1,end+1);CalculateHeight(array,sa,n);int ans=BinSearch(0,n,m,n);printf("%d\n",ans);}return 0;}