Longest Common Substring

http://acm.hdu.edu.cn/showproblem.php?pid=1403

题解：后缀数组+最长公共子串

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
#define endl "\n"
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=200000+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,p,l,u,v;
int ans,cnt,flag,temp,sum;
int r[N],c[N],x[N],y[N],sa[N],ra[N],height[N];
char str1[N],str2[N];
struct node{};
void SA(int n,int m){
    for(int i=0;i<=m;i++)c[i]=0;
    for(int i=1;i<=n;i++)c[x[i]=r[i]]++;
    for(int i=1;i<=m;i++)c[i]+=c[i-1];
    for(int i=n;i>=1;i--)sa[c[x[i]]--]=i;
    for(int k=1;k<=n;k<<=1){
        int num=0;
        for(int i=n-k+1;i<=n;i++)y[++num]=i;
        for(int i=1;i<=n;i++)if(sa[i]>k)y[++num]=sa[i]-k;
        for(int i=0;i<=m;i++)c[i]=0;
        for(int i=1;i<=n;i++)c[x[i]]++;
        for(int i=1;i<=m;i++)c[i]+=c[i-1];
        for(int i=n;i>=1;i--)sa[c[x[y[i]]]--]=y[i],y[i]=0;
        swap(x,y);
        x[sa[1]]=1;
        num=1;
        for(int i=2;i<=n;i++)
            x[sa[i]]=(y[sa[i]]==y[sa[i-1]]&&y[sa[i]+k]==y[sa[i-1]+k])?num:++num;
        if(num==n)
            break;
        m=num;
    }
}
void getheight(int n){
    int k=0;
    for(int i=1;i<=n;i++)ra[sa[i]]=i;
    for(int i=1;i<=n;i++){
        if(k)k--;
        int j=sa[ra[i]-1];
        while(r[i+k]==r[j+k])k++;
        height[ra[i]]=k;
    }
}
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);
    //scanf("%d",&t);
    //while(t--){
    //scanf("%d",&n);
    while(~scanf("%s%s",str1+1,str2+1)){
        int len1=strlen(str1+1);
        int len2=strlen(str2+1);
        for(int i=1;i<=len1;i++)r[i]=str1[i]-'a'+1;
        r[len1+1]=27;
        for(int i=1;i<=len2;i++)r[i+len1+1]=str2[i]-'a'+1;
        int len=len1+len2+2;
        r[len]=0;
        SA(len,27);
        getheight(len);
        ans=-INF;
        for(int i=2;i<=len;i++){
            if((sa[i]<=len1)!=(sa[i-1]<=len1)){
                ans=max(ans,height[i]);
            }
        }
        cout<<ans<<endl;
    }

    //}

#ifdef DEBUG
	printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
    //cout << "Hello world!" << endl;
    return 0;
}