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题解
两遍dfs
#include<iostream>
#include<vector>
#include<cstdio>
#include<set>
#include<cstring>
using namespace std;
const int MAXN = 1e4 + 10;
vector<int> t;
bool vis[MAXN];
vector<vector<int>> e;
set<int> res;
int n, k;
int deepest;
void dfs(int deep, int u) {
if(deep > deepest) {
deepest = deep;
t.clear();
t.push_back(u);
} else if(deepest == deep) {
t.push_back(u);
}
vis[u] = true;
for(int v = 0; v < e[u].size(); ++v) if(vis[e[u][v]] == false) dfs(deep + 1, e[u][v]);
}
int main() {
scanf("%d", &n);
e.resize(n + 1);
int a, b;
for(int i = 0; i < n - 1; ++i) {
scanf("%d%d", &a, &b);
e[a].push_back(b); e[b].push_back(a);
}
int s = 0;
for(int i = 1; i <= n; ++i) {
if(vis[i] == false) {
dfs(1, i);
if(i == 1) {
for(int j = 0; j < t.size(); ++j) {
res.insert(t[j]);
s = t[j];
}
}
++k;
}
}
if(k >= 2) printf("Error: %d components", k);
else {
t.clear();
memset(vis, 0, sizeof(vis));
dfs(1, s);
for(int i = 0; i < t.size(); ++i) res.insert(t[i]);
for(set<int>::iterator it = res.begin(); it != res.end(); ++it) printf("%d\n", *it);
}
return 0;
}