A1021 Deepest Root
摘要
Title: A1021 Deepest Root
Tag: 并查集、DFS
Memory Limit: 64 MB
Time Limit: 1000 ms
Powered by:NEFU AB-IN
A1021 Deepest Root
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题意
A graph which is connected and acyclic can be considered a tree. The height of the tree depends on the selected root. Now you are supposed to find the root that results in a highest tree. Such a root is called the deepest root.
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思路
先并查集进行找连通块，之后DFS求最深深度
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代码
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100/*
* @Author: NEFU AB-IN
* @Date: 2022-09-12 19:01:41
* @FilePath: \GPLT\A1021\A1021.cpp
* @LastEditTime: 2022-09-12 19:33:53
*/
using namespace std;
typedef pair<int, int> PII;
const int N = 1e5 + 10;
int fa[N];
vector<int> g[N];
int find(int x)
{
if (fa[x] != x)
fa[x] = find(fa[x]);
return fa[x];
}
int dfs(int fa, int u)
{
int d = 0;
for (auto v : g[u])
{
if (v == fa)
continue;
d = max(d, dfs(u, v) + 1);
}
return d;
}
signed main()
{
int n;
scanf("%d", &n);
for (int i = 1; i <= n; ++i)
{
fa[i] = i;
}
for (int i = 1; i < n; ++i)
{
int u, v;
scanf("%d%d", &u, &v);
g[u].push_back(v);
g[v].push_back(u);
if (find(u) != find(v))
{
fa[find(u)] = find(v);
}
}
int cnt = 0;
for (int i = 1; i <= n; ++i)
{
if (fa[i] == i)
cnt++;
}
if (cnt > 1)
{
printf("Error: %d components", cnt);
return 0;
}
vector<int> ans;
int mx = 0;
for (int i = 1; i <= n; ++i)
{
int d = dfs(-1, i);
if (d > mx)
{
mx = d;
ans.clear();
ans.push_back(i);
}
else if (d == mx)
ans.push_back(i);
}
printf("%d", ans[0]);
for (int i = 1; i < SZ(ans); ++i)
{
printf("\n%d", ans[i]);
}
return 0;
}