poj1743(后缀数组+二分) (一)

[cpp]
#include
#include
#define N 1000010

int wa[N],wb[N],wv[N],ws[N];
int rank[N],height[N];
int sa[N],r[N];

int max(int a,int b)
{
return a>b a:b;
}

int min(int a,int b)
{
return a }

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

void da(int *r,int *sa,int n,int m)
{
int i,j,p,*x=wa,*y=wb,*t;
for(i=0; i for(i=0; i for(i=1; i for(i=n-1; i>=0; i--) sa[--ws[x[i]]]=i;
for(p=1,j=1; p {
for(p=0,i=n-j; i for(i=0; i=j) y[p++]=sa[i]-j;
for(i=0; i for(i=0; i for(i=0; i for(i=1; i for(i=n-1; i>=0; i--)
sa[--ws[wv[i]]]=y[i];
for(t=x,x=y,y=t,p=1,x[sa[0]]=0,i=1; i x[sa[i]]=cmp(y,sa[i-1],sa[i],j) p-1:p++;
}
}

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

bool check(int k,int n)
{
int i;
int min_val=sa[1],max_val=sa[1];
for(i=2;i<=n;i++)
{
if(height[i] else
{
min_val=min(min_val,sa[i]);
max_val=max(max_val,sa[i]);
if(max_val-min_val>=k) return true;
}
}
return false;
}

int Binary(int st,int ed,int n)
{
int l=st,r=ed,mid;
while(l {
mid=(l+r+1)/2;
if(check(mid,n)) l=mid;
else r=mid-1;
}
return l;
}

int main()
{
int i,n,a,b;
while(~scanf("%d",&n),n)
{
scanf("%d",&b);
for(i=0;i {
scanf("%d",&a);
r[i]=a-b+88;
b=a;
}
r[n-1]=0;
da(r,sa,n,300);
calheight(r,sa,n-1);
n--;
int ans=Binary(0,n/2,n);
if(ans>=4) printf("%d\n",ans+1);
else puts("0");
}
return 0;
}