189 lines
3.9 KiB
C++
189 lines
3.9 KiB
C++
/* Problem URL: https://codeforces.com/contest/903/problem/E */
|
|
|
|
#include <bits/stdc++.h>
|
|
#include <ext/pb_ds/assoc_container.hpp>
|
|
#include <ext/pb_ds/tree_policy.hpp>
|
|
|
|
using namespace std;
|
|
using namespace __gnu_pbds;
|
|
|
|
template <class T, class comp = less<>>
|
|
using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;
|
|
|
|
#define V vector
|
|
|
|
#define rmin(a, b) a = min(a, b)
|
|
#define rmax(a, b) a = max(a, b)
|
|
|
|
#define rep(i, lim) for (int i = 0; i < (lim); i++)
|
|
#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
|
|
|
|
#define repv(i, v) for (auto &i : (v))
|
|
#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
|
|
#define sortv(v) sort(v.begin(), v.end())
|
|
#define all(v) (v).begin(), (v).end()
|
|
|
|
using vi = vector<int>;
|
|
using vvi = vector<vi>;
|
|
using vvvi = vector<vvi>;
|
|
using vvvvi = vector<vvvi>;
|
|
|
|
using ll = long long;
|
|
|
|
using vl = vector<ll>;
|
|
using vvl = vector<vl>;
|
|
using vvvl = vector<vvl>;
|
|
using vvvvl = vector<vvvl>;
|
|
|
|
template<class v>
|
|
auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
|
|
os << vec[0];
|
|
for (size_t i = 1; i < vec.size(); i++) {
|
|
os << ' ' << vec[i];
|
|
}
|
|
os << '\n';
|
|
return os;
|
|
}
|
|
|
|
template<class v>
|
|
auto operator>>(istream &is, vector<v> &vec)->istream& {
|
|
for (auto &i : vec) {
|
|
is >> i;
|
|
}
|
|
return is;
|
|
}
|
|
|
|
template<class v>
|
|
auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
|
|
for (auto &i : vec) {
|
|
os << i[0];
|
|
for (size_t j = 1; j < i.size(); j++) {
|
|
os << ' ' << i[j];
|
|
}
|
|
os << '\n';
|
|
}
|
|
return os;
|
|
}
|
|
|
|
template<class v>
|
|
auto operator>>(istream &is, vector<vector<v>> &vec)->istream& {
|
|
for (auto &i : vec) {
|
|
for (auto &j : i) {
|
|
is >> j;
|
|
}
|
|
}
|
|
return is;
|
|
}
|
|
|
|
int main()
|
|
{
|
|
ios::sync_with_stdio(false);
|
|
cin.tie(nullptr);
|
|
|
|
int n, k;
|
|
cin >> k >> n;
|
|
|
|
V<string> fds(k);
|
|
cin >> fds;
|
|
|
|
vi diffs;
|
|
|
|
int other = 0;
|
|
|
|
vi c1(26);
|
|
rep(i, n) {
|
|
c1[fds[0][i] - 'a']++;
|
|
}
|
|
|
|
nrep(i, 1, k) {
|
|
vi c2(26);
|
|
rep(j, n) {
|
|
if (fds[0][j] != fds[i][j]) {
|
|
diffs.push_back(j);
|
|
}
|
|
c2[fds[i][j] - 'a']++;
|
|
}
|
|
|
|
if (c1 != c2) {
|
|
cout << "-1\n";
|
|
return 0;
|
|
}
|
|
|
|
if (!diffs.empty()) {
|
|
other = i;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (diffs.empty()) {
|
|
swap(fds[0][0], fds[0][1]);
|
|
cout << fds[0] << '\n';
|
|
return 0;
|
|
}
|
|
|
|
if (diffs.size() > 4) {
|
|
cout << "-1\n";
|
|
return 0;
|
|
}
|
|
|
|
string now = fds[0];
|
|
auto test = [&]() {
|
|
rep(i, diffs.size()) {
|
|
rep(j, n) {
|
|
if (diffs[i] == j) {
|
|
continue;
|
|
}
|
|
swap(now[diffs[i]], now[j]);
|
|
|
|
auto diff = [&](string &a, string &b) {
|
|
vi count(26);
|
|
bool lmao = false;
|
|
|
|
int ans = 0;
|
|
rep(i, n) {
|
|
count[a[i] - 'a']++;
|
|
lmao = lmao || count[a[i] - 'a'] >= 2;
|
|
if (a[i] != b[i]) {
|
|
ans++;
|
|
}
|
|
}
|
|
|
|
return ans == 2 || (ans == 0 && lmao);
|
|
};
|
|
|
|
bool pos = true;
|
|
|
|
rep(l, k) {
|
|
int d = diff(now, fds[l]);
|
|
if (!diff(now, fds[l])) {
|
|
pos = false;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (pos) {
|
|
return true;
|
|
}
|
|
|
|
swap(now[diffs[i]], now[j]);
|
|
}
|
|
}
|
|
|
|
return false;
|
|
};
|
|
|
|
if (test()) {
|
|
cout << now << '\n';
|
|
return 0;
|
|
}
|
|
|
|
now = fds[other];
|
|
|
|
if (test()) {
|
|
cout << now << '\n';
|
|
return 0;
|
|
}
|
|
|
|
cout << "-1\n";
|
|
}
|