poj2774 Long Long Message 后缀数组

poj2774 Long Long Message
题意:求两个串的最长公共子串 n<=100000
题解:论文题&&模板题不多说了= =

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=200005;
int sa[N],c[N],t1[N],t2[N];
int rank[N],height[N];
char s1[N],s2[N],s[N];
int n;
bool pos[N];
//rank[i] i串排名
//sa[i] 第i的串为 
void buildsa(int m){
    int i,*x=t1,*y=t2;
    for(i=1;i<=m;i++) c[i]=0;
    for(i=1;i<=n;i++) c[x[i]=s[i]]++;
    for(i=1;i<=m;i++) c[i]+=c[i-1];
    for(i=n;i>=1;i--) sa[c[x[i]]--]=i;
    for(int k=1;k<=n;k<<=1){
        int p=0;
        for(i=n-k+1;i<=n;i++) y[++p]=i;
        for(i=1;i<=n;i++) if(sa[i]>k) y[++p]=sa[i]-k;
        for(i=1;i<=m;i++) c[i]=0;
        for(i=1;i<=n;i++) c[x[y[i]]]++;
        for(i=1;i<=m;i++) c[i]+=c[i-1];
        for(i=n;i>=1;i--) sa[c[x[y[i]]]--]=y[i];
        swap(x,y);p=1;x[sa[1]]=1;
        for(i=2;i<=n;i++)
            x[sa[i]]=y[sa[i]]==y[sa[i-1]]&&y[sa[i]+k]==y[sa[i-1]+k]?p:++p;
        if(p>=n) break;
        m=p;
    }
}
void getheight(){
    int i,j,k=0;
    for(i=1;i<=n;i++) rank[sa[i]]=i;
    for(i=1;i<=n;i++){
        if(k) k--;
        j=sa[rank[i]-1];
        while(s[i+k]==s[j+k]) k++;
        height[rank[i]]=k;
    }
}
int main(){
    freopen("in.txt","r",stdin);
    freopen("out.txt","w",stdout);
    scanf("%s\n",s+1);scanf("%s\n",s2);int l=strlen(s+1);
    strcat(s+1,"#");strcat(s+1,s2);//printf("%s\n",s+1);
    n=strlen(s+1);//printf("%d\n",n);
    buildsa(128);getheight();
    for(int i=1;i<=n;i++) pos[i]=sa[i]<=l?1:0;
    int ans=0;
    for(int i=2;i<=n;i++)
        if(pos[i]!=pos[i-1]) ans=max(ans,height[i]);
    printf("%d\n",ans);
    return 0;
}