不小于k个字符串的最长子串

题目链接：https://cn.vjudge.net/contest/318888#problem/K

题意：

给你n个字符串，求至少出现在向上取整n/2的个串的公共子串如果有多个就输出多个。

思路：

#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <queue>
#include <set>

#define INF 0x3f3f3f3f
#define pii pair<int,int>
#define LL long long
using namespace std;
typedef unsigned long long ull;
const int MAXN = 200005;

int wa[MAXN], wb[MAXN], wv[MAXN], ws_[MAXN];
void Suffix(int *r, int *sa, int n, int m)
{
    int i, j, k, *x = wa, *y = wb, *t;
    for(i = 0; i < m; ++i) ws_[i] = 0;
    for(i = 0; i < n; ++i) ws_[x[i] = r[i]]++;
    for(i = 1; i < m; ++i) ws_[i] += ws_[i - 1];
    for(i = n - 1; i >= 0; --i) sa[--ws_[x[i]]] = i;
    for(j = 1, k = 1; k < n; j *= 2, m = k)
    {
        for(k = 0, i = n - j; i < n; ++i) y[k++] = i;
        for(i = 0; i < n; ++i) if(sa[i] >= j) y[k++] = sa[i] - j;
        for(i = 0; i < n; ++i) wv[i] = x[y[i]];
        for(i = 0; i < m; ++i) ws_[i] = 0;
        for(i = 0; i < n; ++i) ws_[wv[i]]++;
        for(i = 1; i < m; ++i) ws_[i] += ws_[i - 1];
        for(i = n - 1; i >= 0; --i) sa[--ws_[wv[i]]] = y[i];
        t = x;
        x = y;
        y = t;
        for(x[sa[0]] = 0, i = k = 1; i < n; ++i)
            x[sa[i]] = (y[sa[i - 1]] == y[sa[i]] && y[sa[i - 1] + j] == y[sa[i] + j]) ? k - 1 : k++;
    }
}
int Rank[MAXN], height[MAXN], sa[MAXN], r[MAXN];
void calheight(int *r,int *sa,int n)
{
    int i,j,k=0;
    for(i=1; i<=n; i++)Rank[sa[i]]=i;
    for(i=0; i<n; height[Rank[i++]]=k)
        for(k?k--:0,j=sa[Rank[i]-1]; r[i+k]==r[j+k]; k++);
}

char s[MAXN];
int vis[MAXN];
int indexx[MAXN];
int T;
vector<int> ans[MAXN];

bool check(int x,int n){
    for (int i=1;i<n;i++) {
        if (height[i] < x)
            continue;
        int cnt = 0;
        for (int j = 0; j <= T; j++) {
            vis[j] = 0;
        }
        while (height[i] >= x && i < n) {
            if (!vis[indexx[sa[i - 1]]]) {
                vis[indexx[sa[i - 1]]] = 1;
                cnt++;
            }
            i++;
        }
        if (!vis[indexx[sa[i - 1]]]) {
            vis[indexx[sa[i - 1]]] = 1;
            cnt++;
        }
        if (cnt > T / 2) {
            ans[x].push_back(sa[i - 1]);
        }
    }
    if(ans[x].size()!=0) return true;
    return false;
}


int main()
{
    while (~scanf("%d",&T) && T) {
        for (int i=0;i<=1000;i++){
            ans[i].clear();
        }
        int XX = 30;
        int n = 0;
        for (int i=0;i<T;i++){
            scanf("%s",s);
            int len = strlen(s);
            for (int j=0;j<len;j++){
                r[n++] = s[j]-'a'+1;
                indexx[n-1] = i;
            }
            r[n++] = XX++;
        }
        r[n] = 0;
        Suffix(r,sa,n+1,250);
        calheight(r,sa,n);
        int L=1,R=1000,mid,len=0;
        while (L<=R){
            mid = (L+R)>>1;
            if (check(mid,n)){
                len = mid;
                L = mid+1;
            }else
                R = mid-1;
        }
        if(len==0) printf("?
");
        else
        {
            for(int i=0;i<ans[len].size();i++)
            {
                for(int j=ans[len][i];j<ans[len][i]+len;j++)
                    printf("%c",(char)r[j]+'a'-1);
                printf("
");
            }
        }
        cout<<endl;
    }
    return 0;
}