Submission #577102

#	Time	Username	Problem	Language	Result	Execution time	Memory
577102		talant117408	Wells (CEOI21_wells)	C++17	0 / 100	18 ms	35540 KiB

wells

#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;

#define long                unsigned long 
#define pb                  push_back
#define mp                  make_pair
#define all(v)              (v).begin(),(v).end()
#define rall(v)             (v).rbegin(),(v).rend()
#define lb                  lower_bound
#define ub                  upper_bound
#define sz(v)               int((v).size())
#define do_not_disturb      ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define endl                '\n'

const int N = 1500007;
vector <int> graph[N];
int well[N], depth[N], n, k;
bool flag;

void dfs(int v = 1, int p = 1) {
    for (auto to : graph[v]) {
        if (to == p) continue;
        depth[to] = depth[v] + 1;
        dfs(to, v);
    }
}

int find_wells(int v = 1, int p = 1) {
    vector <int> depths;
    for (auto to : graph[v]) {
        if (to == p) continue;
        auto res = find_wells(to, v);
        if (res) {
            depths.pb(res);
        }
    }
    sort(rall(depths));
    if ((sz(depths) && depths[0] >= k-1) || (sz(depths) > 1 && depths[0]+depths[1] >= k-1)) {
        well[v] = 1;
        return 0;
    }
    if (sz(depths)) return depths[0]+1;
    else return 1;
}

int find_dbw(int v = 1, int p = 1) {
    vector <int> depths;
    for (auto to : graph[v]) {
        if (to == p) continue;
        auto res = find_dbw(to, v);
        if (res) {
            depths.pb(res);
        }
    }
    sort(all(depths));
    if ((well[v] && sz(depths) && depths[0] < k) || (sz(depths) > 1 && depths[0]+depths[1] < k)) {
        cout << "NO\n0";
        exit(0);
    }
    if (well[v]) return 1;
    else if (sz(depths)) return depths[0]+1;
    else return 0;
}

void solve() {
    cin >> n >> k;
    for (int i = 1; i < n; i++) {
        int a, b;
        cin >> a >> b;
        graph[a].pb(b);
        graph[b].pb(a); 
    }
    dfs();
    find_wells();
    find_dbw(); // distance between wells
    if (flag) cout << "NO\0";
    else cout << "YES\n1";
}

int main() {
    do_not_disturb
    
    int t = 1;
    //~ cin >> t;
    while (t--) {
        solve();
    }
    
    return 0;
}

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