Submission #525524

#	Time	Username	Problem	Language	Result	Execution time	Memory
525524		sidon	K-th path (IZhO11_kthpath)	C++17	100 / 100	1 ms	332 KiB

kthpath

#include <bits/stdc++.h>
using namespace std;
#define int long long

const int Z = 35;

int n, m, k, dp[Z][Z];
string a[Z];

int32_t main() {
	ios::sync_with_stdio(0), cin.tie(0);

	for(int i = 1; i < Z; ++i)
		for(int j = 1; j < Z; ++j)
			dp[i][j] = dp[i-1][j] + dp[i][j-1], dp[1][1] = 1;

	cin >> n >> m;
	for(int i = 0; i < n; ++i)
		cin >> a[i];
	cin >> k;

	string ans(n+m-1, a[0][0]);
	map<array<int, 2>, int> cur, nxt;
	cur[{0, 0}] = 1;

	for(int i = 0; i < n+m-1; ++i) {
		map<char, int> sum;

		for(auto &[j, cnt] : cur) {
			auto [x, y] = j;
			sum[a[x][y]] += dp[n-x][m-y] * cnt;
		}

		for(auto &[c, s] : sum) {
			ans[i] = c;
			if(s < k) k -= s;
			else break;
		}

		for(auto &[j, cnt] : cur) {
			auto [x, y] = j;
			if(a[x][y] == ans[i]) {
				if(x+1 != n) nxt[{x+1, y}] += cnt;
				if(y+1 != m) nxt[{x, y+1}] += cnt;
			}
		}

		cur = nxt;
		nxt.clear();
	}

	cout << ans;
}

• Subtask 1: 100 / 100