Submission #523302

#	Time	Username	Problem	Language	Result	Execution time	Memory
523302		Pety	K-th path (IZhO11_kthpath)	C++14	0 / 100	1 ms	432 KiB

kthpath

#include <bits/stdc++.h>
#define ll long long

using namespace std;

const ll INF = 1e18;
const int MOD = 1e9 + 7;

ifstream fin ("hyper.in");
ofstream fout ("hyper.out");

int n, m, viz[32][32], cnt[32][32];
ll comb[62][62];
ll k;
char ch[32][32];
deque<pair<int, int>>q;

int dl[4] = {0, 0, -1, 1};
int dc[4] = {1, -1, 0, 0};


int main () 
{
  //ios_base::sync_with_stdio(false);
  //cin.tie(0); cout.tie(0);
  cin >> n >> m;
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++)
      cin >> ch[i][j];
  for (int i = 0; i <= n + m; i++) {
    comb[i][0] = comb[i][i] = 1;
    for (int j = 1; j < i; j++)
      comb[i][j] = min(INF, comb[i - 1][j] + comb[i - 1][j - 1]);
  }
  cin >> k;
  viz[1][1] = 1;
  cnt[1][1] = 1;
  q.push_back({1, 1});
  for (int pas = 1; pas <= n + m - 1; pas++) {
    vector<ll>nr(26);
    for (auto p: q) {
      if (INF / cnt[p.first][p.second] < comb[n - p.first + m - p.second][n - p.first])
        nr[ch[p.first][p.second] - 'a'] += INF;
      else 
        nr[ch[p.first][p.second] - 'a'] += 1ll * cnt[p.first][p.second] * comb[n - p.first + m - p.second][n - p.first]; 
      nr[ch[p.first][p.second] - 'a'] = min(nr[ch[p.first][p.second] - 'a'], INF);
    }
    for (int j = 1; j < 26; j++)
      nr[j] = min(INF, nr[j] + nr[j - 1]);
    char letter = 'z' + 1;
    for (int j = 0; j < 26; j++)
      if (k <= nr[j]) {
        letter = j + 'a';
        k -= (j == 0 ? 0 : nr[j - 1]);
        break;
      }
    assert(letter != 'z' + 1);
    cout << letter;
    int sz = q.size();
    for (int i = 1; i <= sz; i++) {
      auto p = q.front();
      q.pop_front();
      if (ch[p.first][p.second] != letter)
        continue;
      for (int k = 0; k < 4; k++) {
        int x = p.first + dl[k];
        int y = p.second + dc[k];
        if (x >= 1 && x <= n && y >= 1 && y <= m) {
          if (!viz[x][y] && x - 1 + y - 1 == pas) {
            q.push_back({x, y});
            viz[x][y] = 1;
            cnt[x][y] = 1;
          }
          else
            cnt[x][y]++;
        } 
      }
    }
  }
    
  return 0;
}

• Subtask 1: 0 / 100