Submission #334182

#	Time	Username	Problem	Language	Result	Execution time	Memory
334182		apostoldaniel854	K-th path (IZhO11_kthpath)	C++14	100 / 100	5 ms	384 KiB

kthpath

#include <bits/stdc++.h>

using namespace std;

using ll = long long;

const int N = 30;

string grid[N];
ll dp[N][N][2];
int n, m;
const ll INF = 1e18;
void add (ll &a, ll b) {
    a += b;
    if (a > INF)
        a = INF;
}


bool check (string &s, ll k) {
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
            for (int k = 0; k < 2; k++)
                dp[i][j][k] = 0;
    if (grid[0][0] < s[0])
        dp[0][0][1] = 1;
    if (grid[0][0] == s[0])
        dp[0][0][0] = 1;
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++) {
            if (s[i + j] > grid[i][j]) {
                if (i)
                    add (dp[i][j][1], dp[i - 1][j][0]), add (dp[i][j][1], dp[i - 1][j][1]);
                if (j)
                    add (dp[i][j][1], dp[i][j - 1][0]), add (dp[i][j][1], dp[i][j - 1][1]);
            }
            else {
                if (i) {
                    if (s[i + j] == grid[i][j])
                        add (dp[i][j][0], dp[i - 1][j][0]);
                    add (dp[i][j][1], dp[i - 1][j][1]);
                }
                if (j) {
                    if (s[i + j] == grid[i][j])
                        add (dp[i][j][0], dp[i][j - 1][0]);
                    add (dp[i][j][1], dp[i][j - 1][1]);
                }
            }
        }
    return dp[n - 1][m - 1][0] + dp[n - 1][m - 1][1] >= k;
}

int main () {
    ios::sync_with_stdio (false);
    cin.tie (0); cout.tie (0);
    cin >> n >> m;
    for (int i = 0; i < n; i++)
        cin >> grid[i];
    ll k;
    cin >> k;
    int sz = n + m - 1;
    string ans (sz, 'z');
    for (int i = 0; i < sz; i++) {
        ans[i] = 'a';
        while (not check (ans, k))
            ans[i]++;
    }
    cout << ans << "\n";
    return 0;
}

• Subtask 1: 100 / 100