Submission #101093

#	Time	Username	Problem	Language	Result	Execution time	Memory
101093		choikiwon	K-th path (IZhO11_kthpath)	C++17	100 / 100	65 ms	512 KiB

kthpath

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

typedef long long ll;

ll comb[63][63];

int N, M;
ll K;
char G[33][33];
string ans;

ll dp[2][33][33];
ll calc() {
    for(int x = (int)ans.size() - 1; x >= 0; x--) {
        int c = x & 1;
        int p = c ^ 1;

        for(int i = 0; i < N; i++) {
            for(int j = 0; j < M; j++) {
                dp[c][i][j] = 0;
                if(G[i][j] != ans[x]) continue;
                if(x == (int)ans.size() - 1) {
                    dp[c][i][j] = comb[N + M - 2 - i - j][M - 1 - j];
                    continue;
                }
                if(i < N - 1) dp[c][i][j] += dp[p][i + 1][j];
                if(j < M - 1) dp[c][i][j] += dp[p][i][j + 1];
            }
        }
    }
    return dp[0][0][0];
}

int main() {
    comb[0][0] = 1;
    for(int i = 1; i < 63; i++) {
        comb[i][0] = 1;
        for(int j = 1; j <= i; j++) {
            comb[i][j] = comb[i - 1][j - 1] + comb[i - 1][j];
        }
    }

    std::ios::sync_with_stdio(false);

    cin >> N >> M;

    for(int i = 0; i < N; i++) {
        for(int j = 0; j < M; j++) {
            cin >> G[i][j];
        }
    }

    cin >> K;

    for(int i = 0; i < N + M; i++) {
        for(int j = 0; j < 26; j++) {
            ans.push_back('a' + j);

            ll t = calc();
            if(K <= t) break;
            K -= t;
            ans.pop_back();
        }
    }

    cout << ans;
}

• Subtask 1: 100 / 100