#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
//#pragma GCC target ("avx2")
//#pragma GCC optimize ("O3")
//#pragma GCC optimize ("unroll-loops")
//#pragma comment (linker, "/STACK: 16777216")
#define f first
#define s second
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((int)(x).size())
#define pb push_back
#define mp make_pair
#define int long long
using namespace std;
using namespace __gnu_pbds;
template <typename T> inline bool umax(T &a, const T &b) { if(a < b) { a = b; return 1; } return 0; }
template <typename T> inline bool umin(T &a, const T &b) { if(a > b) { a = b; return 1; } return 0; }
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
template <typename T> using oset = tree<T, null_type, less <T>, rb_tree_tag, tree_order_statistics_node_update>;
const ll mod = 998244353;
const ll base = 1e6 + 5;
const ll inf = 1e18;
const int MAX = 1e6;
const int lg = 20;
random_device rd;
mt19937 gen(rd());
uniform_int_distribution<ll> dis(1, inf);
void solve() {
int n, m;
cin >> n >> m;
vector<vector<int>> a(n, vector<int>(m));
for(int i = 0; i < n; i++) {
for(int j = 0; j < m; j++) {
char c;
cin >> c;
a[i][j] = c - 'a';
}
}
vector<vector<int>> dp(n, vector<int>(m));
dp[n - 1][m - 1] = 1;
for(int i = n - 1; ~i; i--) {
for(int j = m - 1; ~j; j--) {
if(i) dp[i - 1][j] += dp[i][j];
if(j) dp[i][j - 1] += dp[i][j];
}
}
int k;
cin >> k; k--;
string ans;
vector<vector<int>> dp_back(n, vector<int>(m)), ndp_back(n, vector<int>(m));
ans.pb(char('a' + a[0][0]));
dp_back[0][0] = 1;
for(int it = 1; it < n + m - 1; it++) {
//cnt prefix == ans
vector<int> cnt(26);
for(int i = 0; i < n; i++) {
for(int j = 0; j < m; j++) {
if(i + 1 < n) cnt[a[i + 1][j]] += dp_back[i][j] * dp[i + 1][j];
if(j + 1 < m) cnt[a[i][j + 1]] += dp_back[i][j] * dp[i][j + 1];
}
}
int add = 0;
while(cnt[add] <= k) k -= cnt[add++];
ans.pb(char('a' + add));
for(int i = 0; i < n; i++) {
for(int j = 0; j < m; j++) {
if(i + 1 < n && a[i + 1][j] == add) ndp_back[i + 1][j] += dp_back[i][j];
if(j + 1 < m && a[i][j + 1] == add) ndp_back[i][j + 1] += dp_back[i][j];
}
}
dp_back = ndp_back;
for(int i = 0; i < n; i++) {
for(int j = 0; j < m; j++) {
ndp_back[i][j] = 0;
}
}
}
cout << ans << '\n';
}
signed main() {
// freopen("kthpath.in", "r", stdin); freopen("kthpath.out", "w", stdout);
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int ttt = 1;
// cin >> ttt;
while(ttt--) {
solve();
}
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
212 KB |
Output is correct |
| 2 |
Correct |
1 ms |
328 KB |
Output is correct |
| 3 |
Correct |
1 ms |
340 KB |
Output is correct |
| 4 |
Correct |
1 ms |
212 KB |
Output is correct |
| 5 |
Correct |
1 ms |
336 KB |
Output is correct |
| 6 |
Correct |
1 ms |
336 KB |
Output is correct |
| 7 |
Correct |
1 ms |
340 KB |
Output is correct |
| 8 |
Correct |
1 ms |
296 KB |
Output is correct |
| 9 |
Correct |
0 ms |
212 KB |
Output is correct |
| 10 |
Correct |
1 ms |
340 KB |
Output is correct |
| 11 |
Correct |
1 ms |
340 KB |
Output is correct |
| 12 |
Correct |
1 ms |
340 KB |
Output is correct |
| 13 |
Correct |
1 ms |
340 KB |
Output is correct |
| 14 |
Correct |
1 ms |
340 KB |
Output is correct |
| 15 |
Correct |
1 ms |
340 KB |
Output is correct |
| 16 |
Correct |
2 ms |
328 KB |
Output is correct |
| 17 |
Correct |
1 ms |
340 KB |
Output is correct |
| 18 |
Correct |
1 ms |
340 KB |
Output is correct |
| 19 |
Correct |
1 ms |
332 KB |
Output is correct |
| 20 |
Correct |
1 ms |
340 KB |
Output is correct |
