Submission #523282

#	Time	Username	Problem	Language	Result	Execution time	Memory
523282		cadmiumsky	K-th path (IZhO11_kthpath)	C++14	0 / 100	1 ms	332 KiB

kthpath

#include <bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define x first
#define y second
using namespace std;

const int inf = 1e18 + 10;
const int nmax = 100;
int n, m;
char mat[nmax][nmax];
int comb[nmax][nmax];

static int add(int a, int b) {
  if(a > inf - b)
    return inf;
  return a + b;
}

static vector<pii> move(vector<pii> initial) {
  vector<pii> sol;
  sort(initial.begin(), initial.end());
  auto insert = [&](int x, int y) {
    if(x >= n || y >= m)
      return;
    sol.push_back({x, y});
  };
  for(auto [a, b] : initial)
    insert(a, b + 1);
  int a, b;
  tie(a, b) = initial.back();
  insert(a + 1, b);
  return sol;
}

static void solve(vector<pii> poz, string s, int k) {
  sort(poz.begin(), poz.end(), [&](pii a, pii b) {return mat[a.x][a.y] < mat[b.x][b.y];});
  if(poz.size() == 1 && poz.back() == pii{n - 1, m - 1}) {
    cout << s << mat[n - 1][m - 1] << '\n';
    exit(0);
  }
  char last = 0;
  int sum = 0;
  vector<pii> curr;
  for(auto [a, b] : poz) {
    if(last != mat[a][b]) {
      if(sum >= k)
        solve(move(curr), s + last, k);
      k -= sum;
      last = mat[a][b]; 
      sum = 0;
      curr.resize(0);
    }
    sum = add(sum, comb[n - a + m - b - 2][n - a - 1]);
    curr.push_back({a, b});
  }
  solve(move(curr), s + last, k);
}

signed main() {
  for(int i = 0; i < nmax; i++) {
    comb[i][0] = comb[i][i] = 1;
    for(int j = 1; j < i; j++)
      comb[i][j] = add(comb[i - 1][j], comb[i - 1][j - 1]);
  }
  cin >> n >> m;
  //cout << n << ' ' << m << '\n';
  for(int i = 0; i < n; i++) {
    for(int j = 0; j < m; j++) {
      cin >> mat[i][j];
    }
    //cout << i << ' ' << n << '\n';
  }
  int k;
  cin >> k;
  vector<pii> v;
  v.push_back({0,0});
  solve(v, "", k);
}

Compilation message (stderr)

kthpath.cpp: In function 'std::vector<std::pair<long long int, long long int> > move(std::vector<std::pair<long long int, long long int> >)':
kthpath.cpp:28:12: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   28 |   for(auto [a, b] : initial)
      |            ^
kthpath.cpp: In function 'void solve(std::vector<std::pair<long long int, long long int> >, std::string, long long int)':
kthpath.cpp:45:12: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   45 |   for(auto [a, b] : poz) {
      |            ^

• Subtask 1: 0 / 100