POJ 2774（后缀数组）

(http://acm.hust.edu.cn/vjudge/contest/view.action?cid=105595#problem/I)
题意：寻找字符串A,B的最长相同子串
解法：构造个后缀数组，随便搞一搞就好了。感觉用Hash+二分也该也能做，太懒了不想了。。。

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <queue>
//#include <tr1/unordered_set>
//#include <tr1/unordered_map>
#include <bitset>
//#pragma comment(linker, "/STACK:1024000000,1024000000")

using namespace std;

#define lson l, m, rt<<1
#define rson m+1, r, rt<<1|1
#define inf 1e9
#define debug(a) cout << #a" = " << (a) << endl;
#define debugarry(a, n) for (int i = 0; i < (n); i++) { cout << #a"[" << i << "] = " << (a)[i] << endl; }
#define clr(x, y) memset(x, y, sizeof x)
#define ll long long
#define ull unsigned long long
#define FOR(i,a,b) \
    for(i=a;a<b?i<=b:i>=b;a<b?i++:i--)

const int maxn = 100000*2*2+100;

struct suffix_array{
    char s[maxn];
    int sa[maxn],t[maxn],t2[maxn],c[maxn];
    int n;

    void build_sa(int m)
    {
        int i,*x=t,*y=t2;
        FOR(i,0,m-1) c[i]=0;
        FOR(i,0,n-1) c[x[i]=s[i]]++;
        FOR(i,1,m-1) c[i]+=c[i-1];
        FOR(i,n-1,0) sa[--c[x[i]]]=i;
        for(int k=1;k<=n;k<<=1){
            int p=0;
            FOR(i,n-k,n-1) y[p++]=i;
            FOR(i,0,n-1) if(sa[i]>=k) y[p++]=sa[i]-k;

            FOR(i,0,m-1) c[i]=0;
            FOR(i,0,n-1) c[x[y[i]]]++;

            FOR(i,0,m-1) c[i]+=c[i-1];
            FOR(i,n-1,0) sa[--c[x[y[i]]]]=y[i];

            swap(x,y);
            p=1;
            x[sa[0]]=0;
            FOR(i,1,n-1)
                x[sa[i]]=y[sa[i-1]]==y[sa[i]]&&
                y[sa[i-1]+k]==y[sa[i]+k]?p-1:p++;
            if(p>=n) break;
            m=p;
        }
    }
    int Rank[maxn],height[maxn];
    void getHeight()
    {
        int k=0;
        for(int i=0;i<n;i++) Rank[sa[i]]=i;
        for(int i=0;i<n;i++){
            if(k) k--;
            int j=sa[Rank[i]-1];
            while(s[i+k]==s[j+k]) k++;
            height[Rank[i]]=k;
        }
    }
}su;

char s[maxn],s2[maxn];

int main()
{
    //freopen("input.txt","r",stdin);
    while(~scanf("%s%s",s,s2))
    {
        int len=strlen(s);
        strcat(s,"&");
        strcat(s,s2);
        strcpy(su.s,s);
        su.n=strlen(s)+1;
        su.build_sa(255);
        su.getHeight();
        int ans=0,last1=0,last2=0;
        for(int i=1;i<=su.n;i++)
        {
            if( su.sa[i] <= len )
            {
                last1 = inf;
                last2 = min(last2,su.height[i]);
                ans = max( ans , last2);
            }
            else
            {
                last2 = inf;
                last1 = min(last1,su.height[i]);
                ans = max( ans , last1);
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}