#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define ll long long
#define mp(x, y) make_pair(x, y)
#define sz(v) ((int) (v).size())
#define all(v) (v).begin(), (v).end()
#define MASK(i) (1LL << (i))
#define BIT(x, y) (((x) >> (y)) & 1)
#define pb push_back
#define heap priority_queue
#define max_rng *max_element
#define min_rng *min_element
#define rep(i, n) for(int i = 1, _n = (n); i <= _n; ++i)
#define forn(i, a, b) for(int i = (a), _b = (b); i <= _b; ++i)
#define ford(i, a, b) for(int i = (a), _b = (b); i >= _b; --i)
template <class X, class Y>
inline bool maximize(X &x, Y y) {
return (x < y ? x = y, true : false);
}
template <class X, class Y>
inline bool minimize(X &x, Y y) {
return (x > y ? x = y, true : false);
}
template <class X>
inline void compress(vector<X> &a) {
sort(all(a));
a.resize(unique(all(a)) - a.begin());
}
int ctz(ll x) { return __builtin_ctzll(x); }
int lg(ll x) { return 63 - __builtin_clzll(x); }
int popcount(ll x) { return __builtin_popcount(x); }
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rand(ll l, ll r) {
return l + abs((ll) rng()) % (r - l + 1);
}
const ll oo = (ll) 2e18;
const int inf = (ll) 1e9 + 7, mod = (ll) 1e9 + 7;
const int N = 55, LOG = 16;
void add(int &x, int y) { x += y; if (x >= mod) x -= mod; }
void sub(int &x, int y) { x -= y; if (x < 0) x += mod; }
int n, m;
char a[N][N];
ll k;
ll kCn[N][N];
ll f[N][N];
bool valid[N][N];
int dx[] = {0, 1};
int dy[] = {1, 0};
bool isIn(int x, int y) {
return 1 <= x && x <= n && 1 <= y && y <= m;
}
vector<pair<int, int>> cur[26];
int main(void) {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin >> n >> m;
rep(i, n) rep(j, m) cin >> a[i][j];
cin >> k;
if (k == 1) {
return cout << a[1][1], 0;
}
#define plus(x, y) { x += y; minimize(x, oo); }
#define get(i, j) kCn[i + j - 2][i - 1]
forn(i, 0, n + m) {
kCn[i][0] = 1;
forn(j, 1, i) {
kCn[i][j] = kCn[i-1][j] + kCn[i-1][j-1];
minimize(kCn[i][j], oo);
}
}
// cout << kCn[3][2] << '\n';
string res;
res += a[1][1];
valid[1][1] = true;
forn(len, 2, n + m - 1) {
// cout << "Begin phase:\n";
forn(i, 0, 25) cur[i].clear();
forn(i, 1, n) forn(j, 1, m) {
if (!valid[i][j]) continue;
forn(t, 0, 1) {
int x = i + dx[t];
int y = j + dy[t];
if (!isIn(x, y)) continue;
cur[a[x][y] - 'a'].pb(mp(x, y));
}
}
// cout << len << ' ' << k << '\n';
int real = 0;
forn(i, 0, 25) {
if (!k) break;
compress(cur[i]);
ll total = 0;
// cout << i << ' ' << total << ": ";
for (pair<int, int> nxt : cur[i]) {
// cout << "(" << n - nxt.fi + 1 << "," << m - nxt.se + 1 << "): " << get(n - nxt.fi + 1, m - nxt.se + 1) << "\n";
plus(total, get(n - nxt.fi + 1, m - nxt.se + 1));
}
// cout << "\n";
if (total < k) k -= total;
else {
real = i;
break;
}
}
res += ((char) (real + 'a'));
memset(valid, 0, sizeof valid);
for (pair<int, int> nxt : cur[real])
valid[nxt.fi][nxt.se] = true;
// cout << "End phase\n\n";
}
cout << res;
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
348 KB |
Output is correct |
| 2 |
Correct |
1 ms |
348 KB |
Output is correct |
| 3 |
Correct |
1 ms |
348 KB |
Output is correct |
| 4 |
Incorrect |
0 ms |
348 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
