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

 

 

 

思路：

 

  1 #include <stdio.h>
  2 #include <iostream>
  3 #include <algorithm>
  4 #include <string.h>
  5 #include <stdlib.h>
  6 #include <math.h>
  7 #include <queue>
  8 #include <set>
  9 
 10 #define INF 0x3f3f3f3f
 11 #define pii pair<int,int>
 12 #define LL long long
 13 using namespace std;
 14 typedef unsigned long long ull;
 15 const int MAXN = 2e5 + 10;
 16 int t;
 17 int wa[MAXN], wb[MAXN], wv[MAXN], ws_[MAXN];
 18 void Suffix(int *r, int *sa, int n, int m)
 19 {
 20     int i, j, k, *x = wa, *y = wb, *t;
 21     for(i = 0; i < m; ++i) ws_[i] = 0;
 22     for(i = 0; i < n; ++i) ws_[x[i] = r[i]]++;
 23     for(i = 1; i < m; ++i) ws_[i] += ws_[i - 1];
 24     for(i = n - 1; i >= 0; --i) sa[--ws_[x[i]]] = i;
 25     for(j = 1, k = 1; k < n; j *= 2, m = k)
 26     {
 27         for(k = 0, i = n - j; i < n; ++i) y[k++] = i;
 28         for(i = 0; i < n; ++i) if(sa[i] >= j) y[k++] = sa[i] - j;
 29         for(i = 0; i < n; ++i) wv[i] = x[y[i]];
 30         for(i = 0; i < m; ++i) ws_[i] = 0;
 31         for(i = 0; i < n; ++i) ws_[wv[i]]++;
 32         for(i = 1; i < m; ++i) ws_[i] += ws_[i - 1];
 33         for(i = n - 1; i >= 0; --i) sa[--ws_[wv[i]]] = y[i];
 34         t = x;
 35         x = y;
 36         y = t;
 37         for(x[sa[0]] = 0, i = k = 1; i < n; ++i)
 38             x[sa[i]] = (y[sa[i - 1]] == y[sa[i]] && y[sa[i - 1] + j] == y[sa[i] + j]) ? k - 1 : k++;
 39     }
 40 }
 41 int Rank[MAXN], height[MAXN], sa[MAXN], r[MAXN];
 42 char s[MAXN];
 43 int indexx[MAXN],vis[200];
 44 void calheight(int *r,int *sa,int n)
 45 {
 46     int i,j,k=0;
 47     for(i=1; i<=n; i++)Rank[sa[i]]=i;
 48     for(i=0; i<n; height[Rank[i++]]=k)
 49         for(k?k--:0,j=sa[Rank[i]-1]; r[i+k]==r[j+k]; k++);
 50 }
 51 
 52 bool check(int x,int n){
 53     int tot = 0;
 54     memset(vis,0, sizeof(vis));
 55     for (int i=1;i<n;i++){
 56         if (height[i]>=x){
 57             for (int j=0;j<t;j++) {
 58                 if (indexx[sa[i]] == j) {
 59                     tot += (vis[j] ? 0 : 1);
 60                     vis[j] = 1;
 61                 }
 62                 if (indexx[sa[i - 1]] == j) {
 63                     tot += (vis[j] ? 0 : 1);
 64                     vis[j] = 1;
 65                 }
 66             }
 67         }
 68         else{
 69             if (tot>=t)
 70                 return true;
 71             tot = 0;
 72             memset(vis,0, sizeof(vis));
 73         }
 74     }
 75     if (tot>=t)
 76         return true;
 77     return false;
 78 }
 79 
 80 
 81 int main()
 82 {
 83     int T;
 84     scanf("%d",&T);
 85     while (T--) {
 86         scanf("%d",&t);
 87         int XX = 1;
 88         int n = 0;
 89         for (int i=0;i<t;i++){
 90             scanf("%s",s);
 91             int len = strlen(s);
 92             for (int j=0;j<len;j++){
 93                 r[n++] = s[j];
 94                 indexx[n-1] = i;
 95             }
 96             indexx[n] = i;
 97             r[n++] = 128+XX++;
 98             reverse(s,s+len);
 99             for (int j=0;j<len;j++){
100                 r[n++] = s[j];
101                 indexx[n-1] = i;
102             }
103             indexx[n] = i;
104             r[n++] = 128+XX++;
105         }
106         r[n] = 0;
107         Suffix(r,sa,n+1,128+XX+1);
108         calheight(r,sa,n);
109         int L=1,R=n,mid,len=0;
110         while (L<=R){
111             mid = (L+R)>>1;
112             if (check(mid,n)){
113                 len = mid;
114                 L = mid+1;
115             }else
116                 R = mid-1;
117         }
118         printf("%d\n",len);
119     }
120     return 0;
121 }