이 제출은 이전 버전의 oj.uz에서 채점하였습니다. 현재는 제출 당시와는 다른 서버에서 채점을 하기 때문에, 다시 제출하면 결과가 달라질 수도 있습니다.
#include <bits/stdc++.h>
using namespace std;
#define int long long
int n, leaves[500005], tot = 0;
bool visited[500005];
vector<int> g[500005];
vector<int> st[500005];
vector<int> ans;
void dfs(int v, int p) {
if (g[v].size() == 1) {
leaves[v] = 1;
}
for (const int u : g[v]) {
if (u != p) {
dfs(u, v);
leaves[v] += leaves[u];
}
}
}
int centroid(int v, int p) {
for (const int u : g[v]) {
if (u != p) {
if (leaves[u] * 2 > tot)
return centroid(u, v);
}
}
return v;
}
void dfs2(int v, int p, int i) {
if (g[v].size() == 1) {
st[i].push_back(v);
}
for (const int u : g[v]) {
if (u != p) {
dfs2(u, v, i);
}
}
}
int32_t main() {
cin >> n;
for (int i = 1; i < n; i++) {
int u, v; cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
for (int i = 1; i <= n; i++) if (g[i].size() == 1) tot++;
dfs(1, 1);
int cent = centroid(1, 1);
for (int i = 0; i < g[cent].size(); i++) {
dfs2(g[cent][i], cent, i);
}
int cnt = (tot + 1) / 2;
ans.resize(cnt * 2);
int idx = 0;
for (int i = 0; i < g[cent].size(); i++) {
for (const int u : st[i]) {
ans[idx] = u;
idx += 2;
if (idx >= cnt * 2) idx = 1;
}
}
if (ans.back() == 0) ans.back() = st[0][0];
cout << cnt << '\n';
for (int i = 0; i < ans.size(); i += 2) {
cout << ans[i] << ' ' << ans[i + 1] << '\n';
}
}
컴파일 시 표준 에러 (stderr) 메시지
net.cpp: In function 'int32_t main()':
net.cpp:56:20: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
56 | for (int i = 0; i < g[cent].size(); i++) {
| ~~^~~~~~~~~~~~~~~~
net.cpp:63:20: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
63 | for (int i = 0; i < g[cent].size(); i++) {
| ~~^~~~~~~~~~~~~~~~
net.cpp:74:20: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
74 | for (int i = 0; i < ans.size(); i += 2) {
| ~~^~~~~~~~~~~~
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