poj 2774 Long Long Message 后缀数组

题目链接

求两个字符串的最长公共子串。

将两个字符串连接起来， 然后找height的最大值， 还要注意此时的sa[i]和sa[i-1]不能在同一个串中。

#include <iostream>
#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <queue>
#include <stack>
#include <bitset>
using namespace std;
#define pb(x) push_back(x)
#define ll long long
#define mk(x, y) make_pair(x, y)
#define lson l, m, rt<<1
#define mem(a) memset(a, 0, sizeof(a))
#define rson m+1, r, rt<<1|1
#define mem1(a) memset(a, -1, sizeof(a))
#define mem2(a) memset(a, 0x3f, sizeof(a))
#define rep(i, n, a) for(int i = a; i<n; i++)
#define fi first
#define se second
typedef pair<int, int> pll;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int mod = 1e9+7;
const int inf = 1061109567;
const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
const int maxn = 2e5+5;
int sa[maxn];
int t1[maxn],t2[maxn],c[maxn], a[maxn];
int rankk[maxn],height[maxn];
void build_sa(int s[],int n,int m)
{
    int i,j,p,*x=t1,*y=t2;
    for(i=0;i<m;i++)c[i]=0;
    for(i=0;i<n;i++)c[x[i]=s[i]]++;
    for(i=1;i<m;i++)c[i]+=c[i-1];
    for(i=n-1;i>=0;i--)sa[--c[x[i]]]=i;
    for(j=1;j<=n;j<<=1)
    {
        p=0;
        for(i=n-j;i<n;i++)y[p++]=i;
        for(i=0;i<n;i++)if(sa[i]>=j)y[p++]=sa[i]-j;
        for(i=0;i<m;i++)c[i]=0;
        for(i=0;i<n;i++)c[x[y[i]]]++;
        for(i=1;i<m;i++)c[i]+=c[i-1];
        for(i=n-1;i>=0;i--)sa[--c[x[y[i]]]]=y[i];
        swap(x,y);
        p=1;x[sa[0]]=0;
        for(i=1;i<n;i++)
            x[sa[i]]=y[sa[i-1]]==y[sa[i]] && y[sa[i-1]+j]==y[sa[i]+j]?p-1:p++;
        if(p>=n)break;
        m=p;
    }
}
void getHeight(int s[],int n)
{
    int i,j,k=0;
    for(i=0;i<=n;i++)rankk[sa[i]]=i;
    for(i=0;i<n;i++)
    {
        if(k)k--;
        j=sa[rankk[i]-1];
        while(s[i+k]==s[j+k])k++;
        height[rankk[i]]=k;
    }
}
int main()
{
    int n, m, t;
    string s, str;
    cin>>s>>str;
    n = s.size();
    for(int i = 0; i<n; i++) {
        a[i] = s[i]-'a';
    }
    a[n] = 27;
    for(int i = 0; i<str.size(); i++) {
        a[i+n+1] = str[i]-'a';
    }
    build_sa(a, n+1+str.size()+1, 28);
    getHeight(a, n+1+str.size());
    int maxx = 0;
    for(int i = 2; i<=n+1+str.size(); i++) {
        if(height[i]>maxx) {
            if(sa[i-1]<n&&sa[i]>n)
                maxx = height[i];
            if(sa[i]<n&&sa[i-1]>n)
                maxx = height[i];
        }
    }
    cout<<maxx<<endl;
    return 0;
}