//Sylwia Sapkowska
#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
using namespace std;
void __print(int x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << "'" << x << "'";}
void __print(const char *x) {cerr << '"' << x << '"';}
void __print(const string &x) {cerr << '"' << x << '"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ", "; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? ", " : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifdef LOCAL
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
#define int long long
typedef pair<int, int> T;
const int oo = 1e18, oo2 = 1e9+7, K = 30;
const int mod = 998244353;
void solve(){
int n, m; cin >> n >> m;
if (m >= n){
cout << "NO\n";
return;
}
vector<vector<int>>g(n+1);
for (int i = 1; i<n; i++){
int a, b; cin >> a >> b;
g[a].emplace_back(b);
g[b].emplace_back(a);
}
vector<int>depth(n+1), par(n+1);
function<void(int, int, int)>dfs = [&](int v, int pa, int pa2=-1){
par[v] = pa;
for (auto x: g[v]){
if (x == pa || x == pa2) continue;
depth[x] = depth[v]+1;
dfs(x, v, -1);
}
};
dfs(1, 1, -1);
T now = {-oo, -oo};
for (int v = 1; v <= n; v++) now = max(now, T{depth[v], v});
int L = now.second;
depth[L] = 0;
dfs(L, L, -1);
now = {-oo, -oo};
for (int v = 1; v <= n; v++) now = max(now, T{depth[v], v});
int R = now.second;
vector<int>curr;
int v = R;
while (1){
curr.emplace_back(v);
if (v == L) break;
v = par[v];
}
reverse(curr.begin(), curr.end());
debug(curr);
int s = (int)curr.size();
for (int rep = 0; rep < s; rep++){
int v = curr[rep];
depth[v] = 0;
dfs(v, (rep ? curr[rep-1] : -1), (rep+1<s ? curr[rep+1] : -1));
}
debug(depth);
if (*max_element(depth.begin(), depth.end()) > 2) {
cout << "NO\n";
return;
}
//fajna struktura drzewa miau
cout << "YES\n";
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
//cin >> t;
while (t--) solve();
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
0 ms |
348 KB |
Unexpected end of file - int32 expected |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
0 ms |
344 KB |
Unexpected end of file - int32 expected |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
0 ms |
348 KB |
Unexpected end of file - int32 expected |
| 2 |
Halted |
0 ms |
0 KB |
- |
