POJ 3080 后缀数组/KMP

题目链接：http://poj.org/problem?id=3080

题意：给定n个DNA串，求最长公共子串。如果最长公共子串的长度小于3时输出no significant commonalities，否则输出该子串，如有多解请输出字典序最小的解

思路：是POJ 3405的弱化版。思路请参考

#define _CRT_SECURE_NO_DEPRECATE
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<time.h>
#include<cmath>
#include<set>
using namespace std;
typedef long long int LL;
const int MAXN =  + ;
int wa[MAXN], wb[MAXN], wv[MAXN], WS[MAXN];
int cmp(int *r, int a, int b, int l)
{
    return r[a] == r[b] && r[a + l] == r[b + l];
}
void da(int *r, int *sa, int n, int m)
{
    int i, j, p, *x = wa, *y = wb, *t;
    for (i = ; i < m; i++) WS[i] = ;
    for (i = ; i < n; i++) WS[x[i] = r[i]]++;
    for (i = ; i < m; i++) WS[i] += WS[i - ];
    for (i = n - ; i >= ; i--) sa[--WS[x[i]]] = i;
    for (j = , p = ; p < n; j *= , m = p)
    {
        for (p = , i = n - j; i < n; i++) y[p++] = i;
        for (i = ; i < n; i++) if (sa[i] >= j) y[p++] = sa[i] - j;
        for (i = ; i < n; i++) wv[i] = x[y[i]];
        for (i = ; i < m; i++) WS[i] = ;
        for (i = ; i < n; i++) WS[wv[i]]++;
        for (i = ; i < m; i++) WS[i] += WS[i - ];
        for (i = n - ; i >= ; i--) sa[--WS[wv[i]]] = y[i];
        for (t = x, x = y, y = t, p = , x[sa[]] = , i = ; i < n; i++)
            x[sa[i]] = cmp(y, sa[i - ], sa[i], j) ? p -  : p++;
    }
    return;
}
int Rank[MAXN], height[MAXN], sa[MAXN];
void calheight(int *r, int *sa, int n){
    int i, j, k = ;
    for (i = ; i <= n; i++) { Rank[sa[i]] = i; }
    for (i = ; i < n; height[Rank[i++]] = k){
        for (k ? k-- : , j = sa[Rank[i] - ]; r[i + k] == r[j + k]; k++);
    }
    return;
}
int r[MAXN], len, n, t, Index[MAXN], pos[ + ];
char str[ + ];
bool check(int x){
    set<int>se;
    for (int i = ; i < len; i++){
        if (height[i] >= x){
            pos[x] = sa[i];
            se.insert(Index[sa[i]]); se.insert(Index[sa[i - ]]);
        }
        else{
            if (se.size() == n){ return true; } se.clear();
        }
    }
    if (se.size() == n){ return true; }
    return false;
}
void solve(){
    if (n == ){
        printf("%d\n", strlen(str));
        return;
    }
    int L = , R = , mid, ans = ;
    while (R >= L){
        mid = (L + R) / ;
        if (check(mid)){
            ans = mid;
            L = mid + ;
        }
        else{
            R = mid - ;
        }
    }
    if (ans <){
        printf("no significant commonalities\n");
    }
    else{
        for (int i = pos[ans], j = ; j < ans; j++, i++){
            printf("%c", (r[i] - n - ) + 'A');
        }
        printf("\n");
    }
}
int main(){
    //#ifdef kirito
    //    freopen("in.txt", "r", stdin);
    //    freopen("out.txt", "w", stdout);
    //#endif
    //    int start = clock();
    scanf("%d", &t);
    while (t--){
        scanf("%d", &n); len = ;
        for (int i = , val = ; i <= n; i++){
            scanf("%s", &str);
            for (int j = ; j < strlen(str); j++){
                Index[len] = i;
                r[len++] = (str[j] - 'A' + n + );
            }
            Index[len] = i;
            r[len++] = val++;
        }
        da(r, sa, len, );
        calheight(r, sa, len - );
        solve();
    }
    //#ifdef LOCAL_TIME
    //    cout << "[Finished in " << clock() - start << " ms]" << endl;
    //#endif
    return ;
}