Submission #678729

#	Time	Username	Problem	Language	Result	Execution time	Memory
678729		gesgha	Wells (CEOI21_wells)	C++17	0 / 100	5 ms	5076 KiB

wells

#include <bits/stdc++.h>
#define fr(i, a, b) for (int i = a; i <= b; i++)
#define rf(i, a, b) for (int i = a; i >= b; i--)
#define fe(x, y) for(auto& x : y)

#define fi first
#define se second
#define pb push_back

#define pw(x) (1LL << (x))
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()

using namespace std;

template <typename T>
using ve = vector <T>;

template <typename T>
bool umx(T& a, T b) { return a < b ? a = b, 1 : 0; }

template <typename T>
bool umn(T& a, T b) { return a > b ? a = b, 1 : 0; }


using ll = long long;
using pll = pair <ll, ll>;
using pii = pair <int, int>;

const int oo = 2e9;
const ll OO = 2e18;
const int N = 2e5 + 10;

ve <int> G[N];
int up[N][22];
int timer;
int tin[N];
int tout[N];

int n, k;
int clrd[N];
int dep[N];
bool bd = 0;

void dfs1(int u, int p) {
    if (u) dep[u] = dep[p] + 1;
    up[u][0] = p;
    tin[u] = timer++;
    fr(i, 1, 20) up[u][i] = up[up[u][i - 1]][i - 1];
    fe(to, G[u]) if (to != p) dfs1(to, u);
    tout[u] = timer;
}

bool isupper(int u, int v) { return tin[u] <= tin[v] && tout[v] <= tout[u]; }



int lca(int u, int v) {
    if (isupper(u, v)) return u;
    if (isupper(v, u)) return v;
    rf(i, 20, 0) if (!isupper(up[u][i], v)) u = up[u][i];
    return up[u][0];
}

int mxw[N];


void dfs(int u, int p, int dst) {
    mxw[u] = 1;
    if (dst % k == 0) {
        clrd[u] = 1;
        mxw[u] = 0;
    }

    ve <int> v;
    fe(to, G[u]) if (to != p) {
        dfs(to, u, dst + 1);
        if (clrd[u] == 0) {
            umx(mxw[u], mxw[to] + 1);
            v.pb(mxw[to]);
        }
    }
    sort(all(v));
    reverse(all(v));
    if (sz(v) > 1 && v[0] + v[1] + 1 >= k) bd = 1;
//    if (sz(v) > 0 && v[0] + dst >= k) bd = 1;
}


int main() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif // LOCAL
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin >> n >> k;
    fr(i,0, n - 2) {
        int u, v; cin >> u >> v; u--; v--;
        G[u].pb(v);
        G[v].pb(u);
    }
    dfs1(0, 0);
//    cout << "NO\n"; return 0;
    fr(i, 0, n - 1) {
        dfs(i, i, 0);
        ve <int> v;
        fr(j, 0, n - 1) if(clrd[j]) v.pb(j);
        fr(i, 0, n - 1) clrd[i] = 0;
        bool bad = 0;
        if (!bd) {
            fr(x, 0, sz(v) - 1) {
                fr(y, x + 1, sz(v) - 1) {
                    int C = lca(v[x], v[y]);
                    if (dep[v[x]] + dep[v[y]] - 2 * dep[C] + 1 <= k) {
                        bad = 1;
                        break;
                    }
                }
                if (bad) break;
            }
        }
        if(!(bad || bd)) {
            cout << "YES\n1\n";
            exit(0);
        }
        bd = 0;
        fr(i, 0, n - 1) mxw[i] = 0;
    }
    cout << "NO\n0\n";
    return 0;
}

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