Submission #683288

#	Time	Username	Problem	Language	Result	Execution time	Memory
683288		vovamr	K-th path (IZhO11_kthpath)	C++17	0 / 100	4 ms	596 KiB

kthpath

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define fi first
#define se second
#define ll long long
#define ld long double
#define sz(x) ((int)(x).size())
#define all(x) 	(x).begin(), (x).end()
#define pb push_back
#define mpp make_pair
#define ve vector
using namespace std;
using namespace __gnu_pbds;
template<class T> using oset = tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
const ll inf = 1e18; const int iinf = 1e9;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
template <typename T> inline bool chmin(T& a, T b) { return (a > b ? a = b, 1 : 0); }
template <typename T> inline bool chmax(T& a, T b) { return (a < b ? a = b, 1 : 0); }

inline void solve() {
#ifdef LOCAL
	const string NAME = "kthpath";
	ifstream cin(NAME + ".in");
	ofstream cout(NAME + ".out");
#endif

	int n, m;
	cin >> n >> m;
	ve<ve<char>> a(n, ve<char>(m));
	for (auto &i : a) for (auto &j : i) cin >> j;

	ve<ve<ll>> dp(n, ve<ll> (m));
	dp[n - 1][m - 1] = 1;

	for (int i = n - 1; ~i; --i) {
		for (int j = m - 1; ~j; --j) {
			if (i + 1 < n) dp[i][j] += dp[i + 1][j];
			if (j + 1 < m) dp[i][j] += dp[i][j + 1];
		}
	}

	ll k;
	cin >> k;

	string result = "";
	map<string,ve<array<ll,3>>> cand;

	cand[string(1, a[0][0])] = {{dp[0][0], 0, 0}};

	while (sz(result) < n + m - 1) {
		map<string,ve<array<ll,3>>> cur;

		string S = cand.begin()->fi;
		for (auto &[ways, x, y] : cand.begin()->se) {
			if (x + 1 < n) {
				cur[S + a[x + 1][y]].pb({dp[x + 1][y], x + 1, y});
			}
			if (y + 1 < m) {
				cur[S + a[x][y + 1]].pb({dp[x][y + 1], x, y + 1});
			}
		}

		map<string,ve<array<ll,3>>> nw;
		for (auto &[str, vec] : cur) {
			ll tot = 0;
			for (auto &[ways, x, y] : vec) tot += ways;
			if (k > tot) {
				k -= tot;
			}
			else {
				nw[str] = vec;
				break;
			}
		}
		swap(cand, nw);
		result = cand.begin()->fi;
	}
	cout << result;
}

signed main() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	int q = 1; // cin >> q;
	while (q--) solve();
	cerr << fixed << setprecision(3) << "Time execution: " << (double)clock() / CLOCKS_PER_SEC << endl;
}

• Subtask 1: 0 / 100