A - Musical Theme + 二分 

  1 #include <bits/stdc++.h>
  2 using namespace std;
  3 
  4 #define LS 2*i
  5 #define RS 2*i+1
  6 #define UP(i,x,y) for(i=x;i<=y;i++)
  7 #define DOWN(i,x,y) for(i=x;i>=y;i--)
  8 #define MEM(a,x) memset(a,x,sizeof(a))
  9 #define W(a) while(a)
 10 #define gcd(a,b) __gcd(a,b)
 11 #define LL long long
 12 #define N 20005
 13 #define MOD 1000000007
 14 #define INF 0x3f3f3f3f
 15 #define EXP 1e-8
 16 int wa[N],wb[N],wsf[N],wv[N],sa[N];
 17 int rank1[N],height[N],s[N],a[N],n;
 18 char str1[N],str2[N];
 19 //sa:字典序中排第i位的起始位置在str中第sa[i]
 20 //rank:就是str第i个位置的后缀是在字典序排第几
 21 //height：字典序排i和i-1的后缀的最长公共前缀
 22 int cmp(int *r,int a,int b,int k)
 23 {
 24     return r[a]==r[b]&&r[a+k]==r[b+k];
 25 }
 26 void getsa(int *r,int *sa,int n,int m)//n要包含末尾添加的0
 27 {
 28     int i,j,p,*x=wa,*y=wb,*t;
 29     for(i=0; i<m; i++)  wsf[i]=0;
 30     for(i=0; i<n; i++)  wsf[x[i]=r[i]]++;
 31     for(i=1; i<m; i++)  wsf[i]+=wsf[i-1];
 32     for(i=n-1; i>=0; i--)  sa[--wsf[x[i]]]=i;
 33     p=1;
 34     j=1;
 35     for(; p<n; j*=2,m=p)
 36     {
 37         for(p=0,i=n-j; i<n; i++)  y[p++]=i;
 38         for(i=0; i<n; i++)  if(sa[i]>=j)  y[p++]=sa[i]-j;
 39         for(i=0; i<n; i++)  wv[i]=x[y[i]];
 40         for(i=0; i<m; i++)  wsf[i]=0;
 41         for(i=0; i<n; i++)  wsf[wv[i]]++;
 42         for(i=1; i<m; i++)  wsf[i]+=wsf[i-1];
 43         for(i=n-1; i>=0; i--)  sa[--wsf[wv[i]]]=y[i];
 44         t=x;
 45         x=y;
 46         y=t;
 47         x[sa[0]]=0;
 48         for(p=1,i=1; i<n; i++)
 49             x[sa[i]]=cmp(y,sa[i-1],sa[i],j)? p-1:p++;
 50     }
 51 }
 52 void getheight(int *r,int n)//n不保存最后的0
 53 {
 54     int i,j,k=0;
 55     for(i=1; i<=n; i++)  rank1[sa[i]]=i;
 56     for(i=0; i<n; i++)
 57     {
 58         if(k)
 59             k--;
 60         else
 61             k=0;
 62         j=sa[rank1[i]-1];
 63         while(r[i+k]==r[j+k])
 64             k++;
 65         height[rank1[i]]=k;
 66     }
 67 }
 68 int ans;
 69 int fun(int k)
 70 {
 71     int i,maxn,minn;
 72     maxn = minn = sa[1];
 73     UP(i,2,n)
 74     {
 75         if(height[i]>=k && i<n)
 76         {
 77             minn = min(minn,sa[i]);
 78             maxn = max(maxn,sa[i]);
 79             continue;
 80         }
 81         if(maxn-minn>=k) return 1;
 82         maxn = minn = sa[i];
 83     }
 84     return 0;
 85 }
 86 
 87 
 88 int main()
 89 {
 90     int i,j,k;
 91     W((~scanf("%d",&n),n))
 92     {
 93         UP(i,0,n-1)
 94         {
 95             scanf("%d",&s[i]);
 96         }
 97         UP(i,0,n-2)
 98         {
 99             s[i] = s[i+1]-s[i]+100;
100         }
101         s[--n] = 0;
102         getsa(s,sa,n+1,200);
103         getheight(s,n);
104         int l = 4,r = n;
105         W(l<=r)
106         {
107             int mid = (l+r)/2;
108             if(fun(mid))
109             {
110                 ans = mid;
111                 l=mid+1;
112             }
113             else r = mid-1;
114         }
115         ans++;
116         printf("%d\n",ans<5?0:ans);
117     }
118 
119     return 0;
120 }

 

posted @ 2018-09-04 21:45  ouyang_wsgwz  阅读(167)  评论(0)    收藏  举报