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题目

代码

#include <bits/stdc++.h>
using namespace std;
const int N = 1e5+10, M = N*2;
int h[N], e[M], ne[M], idx;
int n;
int ans = 2e9;
bool st[N];
void add(int a, int b)  // 添加一条边a->b
{e[idx] = b, ne[idx] = h[a], h[a] = idx ++ ;
}
int dfs(int u)
{int maxx = 0; int sz = 0; st[u] = true;for(int i = h[u]; ~i; i = ne[i]){int j = e[i];if(st[j]) continue;int s = dfs(j);maxx = max(maxx, s);sz += s;}maxx = max(maxx, n-sz-1);ans = min(ans, maxx);return sz+1;
}
int main()
{cin >> n;memset(h, -1, sizeof h);for(int i = 0; i < n-1; i++){int a, b;cin >> a >> b;add(a, b);add(b, a);}dfs(1);cout << ans;
}

注意