後綴數組模板 poj 2774 Long Long Message

轉載：https://111qqz.com/2016/07/poj-2774/

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <cmath>
#include <cstdlib>
#include <ctime>
#define fst first
#define sec second
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define ms(a,x) memset(a,x,sizeof(a))
typedef long long LL;
#define pi pair < int ,int >
#define MP make_pair
using namespace std;
const double eps = 1E-8;
const int dx4[4]= {1,0,0,-1};
const int dy4[4]= {0,-1,1,0};
const int inf = 0x3f3f3f3f;
const int N=2E5+7;
char s[N];
int sa[N],t[N],t2[N],cnt[N],n;
int c[N];
int w[N];
int rk[N],height[N];
int cmp( int *r,int a,int b,int l)
{
    return r[a]==r[b]&&r[a+l]==r[b+l] ;
};
void build_sa(int n,int m) //其實我覺得。。。sa怎麼得到的不用管。。這部分講道理不會變。。。反正知道能nlogn得到sa就對了2333
{
    int *x=t,*y=t2;
    for ( int i = 0 ; i < m ; i++) c[i] = 0 ;
    for ( int i = 0 ; i < n;  i++) c[x[i]=s[i]]++; //x[i]相當於保存了rank的相對大小，由於只是爲了比較大小，所以沒必要求出真實的rank值。
    for ( int i = 1 ; i < m ; i++) c[i]+=c[i-1];
    for ( int i = n-1 ; i >= 0 ; i--) sa[--c[x[i]]] =  i;
    for ( int k = 1 ; k <= n ; k<<=1)  //進行若干次基數排序，每次對長度爲k的字符串排序
    {
        int p  = 0 ;
        for ( int i = n-k ; i < n ; i++)  y[p++] = i;
        for ( int i = 0 ; i < n ; i++) if (sa[i]>=k) y[p++] = sa[i]-k; //y保存對第二關鍵字排序的結果，可以直接用上一次求得的sa算出。
        for ( int  i = 0 ; i < m  ;  i++) c[i] = 0;
        for ( int i = 0 ; i < n ; i++) c[x[y[i]]]++;
        for ( int i = 0 ; i < m ; i++) c[i]+=c[i-1];
        for ( int i = n-1 ; i >= 0 ; i--) sa[--c[x[y[i]]]] = y[i];
        swap(x,y);
        p = 1;
        x[sa[0]] = 0 ;
        for ( int i = 1 ; i < n ; i++)
            x[sa[i]]= cmp(y,sa[i-1],sa[i],k)?p-1:p++;
        if (p>=n) break;
        m = p;
    }
}
void getHeight( int n)
{
    int k = 0 ;
    for ( int i = 0 ; i < n ; i++) rk[sa[i]] = i;
    height[0] = 0 ;
    for ( int i = 0 ; i < n ; i++)
    {
        if (rk[i]==0) continue;
        if (k) k--;
        int j = sa[rk[i]-1];
        while (s[i+k]==s[j+k]) k++;
        height[rk[i]] = k;
    }
}
int getSuffix(char s[])
{
    int len = strlen(s);
    int up = 0 ;
    for ( int i =  0 ; i < len ; i++)
    {
        w[i] = s[i];
        up = max(up,w[i]);
    }
    w[len++] = 0 ;
    build_sa(len,up+1);
    getHeight(len);
    return len;
}
int main()
{
    string st1,st2,st;
    cin>>st1>>st2;
    int len1 = st1.length();
    st = st1 + "$" + st2;
    strcpy(s,st.c_str());
    int len = getSuffix(s);
    int ans = 0 ;
    for ( int i = 2 ; i < len ; i++)
        if (height[i] > ans)
        {
            if (0 <= sa[i-1] && sa[i-1] < len1 && len1 < sa[i])
                ans = height[i];
            if (0 <= sa[i] && sa[i] < len1 && len1 < sa[i-1])
                ans = height[i];
        }
    printf("%d\n",ans);
    return 0;
}