1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
| #include <bits/stdc++.h>
using namespace std;
using LL = long long;
#define FOR(i, x, y) for (decay<decltype(y)>::type i = (x), _##i = (y); i < _##i; ++i)
#define FORD(i, x, y) for (decay<decltype(x)>::type i = (x), _##i = (y); i > _##i; --i)
#ifdef zerol
#define dbg(args...) do { cout << "\033[32;1m" << #args << " -> "; err(args); } while (0)
#else
#define dbg(...)
#endif
void err() { cout << "\033[39;0m" << endl; }
template<template<typename...> class T, typename t, typename... Args>
void err(T<t> a, Args... args) { for (auto x: a) cout << x << ' '; err(args...); }
template<typename T, typename... Args>
void err(T a, Args... args) { cout << a << ' '; err(args...); }
const int maxn = 1E5 * 4 + 100;
namespace sam {
const int M = maxn;
int t[M][26], len[M] = {-1}, fa[M], sz, last;
int ml[M], ml_fr[M];
int c[M] = {1}, a[M];
bool cnt[M][2];
int pos[M][2], one[M][2];
vector<int> G[M];
void init() {
FOR (i, 1, sz) {
memset(t[i], 0, sizeof t[0]);
memset(cnt[i], 0, sizeof cnt[0]);
memset(pos[i], -1, sizeof pos[0]);
memset(one[i], -1, sizeof one[0]);
ml[i] = c[i] = a[i] = 0;
G[i].clear();
}
sz = 2; last = 1;
}
void re() { last = 1; }
void ins(int ch, int id, int pp) {
int p = last, np = 0, nq = 0, q = -1;
if (!t[p][ch]) {
np = sz++;
len[np] = len[p] + 1;
for (; p && !t[p][ch]; p = fa[p]) t[p][ch] = np;
}
if (!p) fa[np] = 1;
else {
q = t[p][ch];
if (len[p] + 1 == len[q]) fa[np] = q;
else {
nq = sz++; len[nq] = len[p] + 1;
memcpy(t[nq], t[q], sizeof t[0]);
memcpy(one[nq], one[q], sizeof t[0]);
fa[nq] = fa[q];
fa[np] = fa[q] = nq;
for (; t[p][ch] == q; p = fa[p]) t[p][ch] = nq;
}
}
last = np ? np : nq ? nq : q;
cnt[last][id] = 1; pos[last][id] = pp;
}
void rsort() {
FOR (i, 1, sz) c[len[i]]++;
FOR (i, 1, sz) c[i] += c[i - 1];
FOR (i, 1, sz) a[--c[len[i]]] = i;
}
void build() {
FOR (i, 2, sz) G[fa[i]].push_back(i);
}
}
namespace pam {
const int M = maxn;
int t[M][26], fa[M], len[M], rs[M];
int sz, n, last;
int N(int l) {
memset(t[sz], 0, sizeof t[0]);
len[sz] = l;
return sz++;
}
void init() {
rs[n = sz = 0] = -1;
last = N(0);
fa[last] = N(-1);
}
int get_fa(int p) {
while (rs[n - 1 - len[p]] != rs[n]) p = fa[p];
return p;
}
void ins(int ch) {
rs[++n] = ch;
int p = get_fa(last);
if (!t[p][ch]) {
int np = N(len[p] + 2);
fa[np] = t[get_fa(fa[p])][ch];
t[p][ch] = np;
}
last = t[p][ch];
}
}
void add(string& s, char* a, char* b, int la, int ra, int lb, int rb) {
s.clear();
FOR (i, lb, rb) s += b[i];
FOR (i, la, ra) s += a[i];
}
int pa_ml[maxn], pa_ml_fr[maxn];
string go(char* a, char* b) {
sam::init();
int la = strlen(a), lb = strlen(b);
FORD (i, la - 1, -1) sam::ins(a[i] - 'a', 0, i);
sam::re();
FOR (i, 0, lb) sam::ins(b[i] - 'a', 1, i);
sam::cnt[1][1] = 1;
sam::rsort(); sam::build();
{
using namespace sam;
FORD (i, sz - 1, 1) {
int u = sam::a[i];
if (cnt[u][1]) {
cnt[fa[u]][1] |= cnt[u][1];
pos[fa[u]][1] = pos[u][1];
}
}
FOR (i, 1, sz) {
int u = sam::a[i];
if (cnt[u][1]) ml[u] = len[u], ml_fr[u] = pos[u][1];
for (int& v: G[u]) ml[v] = ml[u], ml_fr[v] = ml_fr[u];
}
FOR (i, 1, sz)
if (pos[i][0] != -1) {
pa_ml[pos[i][0]] = ml[i];
pa_ml_fr[pos[i][0]] = ml_fr[i];
}
}
pam::init();
int ans = 0, al = -1, ar = -1, bl = -1, br = -1;
string last, nxt;
pa_ml[la] = 0;
FOR (i, -1, la) {
pam::ins(a[i] - 'a');
int pl = i >= 0 ? pam::len[pam::last] : 0;
int pl2 = pa_ml[i + 1];
int cur = pl + pl2 * 2;
if (pl2 && cur >= ans) {
if (cur == ans) add(last, a, b, al, ar, bl, br);
int arr = i + 1 + pl2, all = arr - pl - pl2;
int brr = pa_ml_fr[i + 1] + 1, bll = brr - pl2;
if (cur == ans) {
add(nxt, a, b, all, arr, bll, brr);
if (last < nxt) continue;
}
ans = cur;
al = all; ar = arr; bl = bll; br = brr;
}
}
add(last, a, b, al, ar, bl, br);
return last;
}
char a[maxn], b[maxn];
int main() {
int T; cin >> T;
memset(sam::pos, -1, sizeof sam::pos);
memset(sam::one, -1, sizeof sam::one);
while (T--) {
scanf("%s%s", a, b);
auto ans1 = go(b, a);
reverse(a, a + strlen(a));
reverse(b, b + strlen(b));
auto ans2 = go(a, b);
string ans = ans1;
if (ans.length() < ans2.length() ||
(ans.length() == ans2.length() && ans > ans2)) ans = ans2;
cout << (ans.empty() ? "-1" : ans) << endl;
}
}
|