Submission #1088196

#	Time	Username	Problem	Language	Result	Execution time	Memory
1088196		MercubytheFirst	Wells (CEOI21_wells)	C++17	0 / 100	1 ms	860 KiB

wells

#include "bits/stdc++.h"
using namespace std;
using ll = long long;
#define endl '\n'

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 37
#endif

const int N = 203;
vector<vector<int> > g;
int n, k;
int dist[N][N];
vector<int> max_dist;
vector<bool> marked;

int dist_calc(const int source, int v, int p) {
    dist[source][v] = dist[source][p] + 1;
    pair<int, int> mx{0, 0};
    for(int to : g[v]) {
        if(to != p) {
            dist_calc(source, to, v);
            mx = max({mx, {mx.first, max_dist[to] + 1}, {max_dist[to] + 1, mx.first}});
        }
    }
    max_dist[v] = mx.first;
    return mx.first + mx.second;
}

bool check_dfs(int v, int p, int d) {
    if(marked[v]) {
        return true;
    }
    if(d + 1 >= k) {
        return false;
    }
    bool ok = true;
    for(int to : g[v]) {
        if(to != p and !marked[to]) {
            ok &= check_dfs(to, v, d + 1);
            if(!ok) {
                break;
            }
        }
    }
    return ok;
}

vector<int> mark_set(int x) {
    vector<int> res;
    marked.assign(n + 1, false);
    for(int i = 1; i <= n; ++i) {
        if(dist[x][i] % k == 0) {
            marked[i] = true;
            res.push_back(i);
        }
    }
    return res;
}

const ll mod = 1e9 + 7;
inline void solve(){
    memset(dist, -1, sizeof(dist));
    cin >> n >> k;
    if(n > 200) {
        cout << "NO\n0\n";
        return;
    }
    g.assign(n + 1, vector<int>());
    for(int i = 1; i < n; ++i) {
        int u, v;
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    vector<bool> useless(n + 1);
    for(int i = 1; i <= n; ++i) {
        max_dist.assign(n + 1, 0);
        int len = dist_calc(i, i, 0);
        if(len + 1 < k) {
            useless[i] = true;
        }
    }
    ll ans = 0;
    if(count(useless.begin() + 1, useless.end(), true) == n) {
        ans = 1;
        for(int i = 1; i <= n; ++i) {
            ans = ans * 2 % mod;
        }
        cout << "YES\n"
             << ans << '\n';
        return;
    }
    for(int u = 1; u <= n; ++u) {
        if(useless[u]) {
            continue;
        }
        vector<int> marked_vertices = mark_set(u);
        const int m = marked_vertices.size();
        bool ok = true;
        for(int i = 0; i < m; ++i) {
            if(marked_vertices[i] < u) {
                ok = false;
                break;
            }
            for(int j = 0; j < i; ++j) {
                if(dist[marked_vertices[i]][marked_vertices[j]] % k) {
                    ok = false;
                    break;
                }
            }
            if(!ok) {
                break;
            }
        }
        for(int i = 1; i <= n; ++i) {
            if(!marked[i] and !check_dfs(i, -1, 0)) {
                assert(false);
                break;
            }
        }
        debug(u, ok);
        ans += ok;
    }
    for(int i = 1; i <= n; ++i) {
        if(useless[i]) {
            ans = ans * 2 % mod;
        }
    }
    cout << (ans ? "YES\n" : "NO\n") << ans << endl;

}

 
signed main(){
    #ifdef LOCAL
    freopen("test.in", "r",  stdin);
    freopen("err.txt", "w", stderr);
    #endif
    ios_base::sync_with_stdio(0);
    cin.tie(NULL); 
    // signed t; cin >> t; while(t--)
        solve();
}

Compilation message (stderr)

wells.cpp: In function 'void solve()':
wells.cpp:9:20: warning: statement has no effect [-Wunused-value]
    9 | #define debug(...) 37
      |                    ^~
wells.cpp:124:9: note: in expansion of macro 'debug'
  124 |         debug(u, ok);
      |         ^~~~~

• Subtask 1: 0 / 30
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 30