C++ 代码

#include <iostream>
#include <vector>
using namespace std;
int n;
vector<vector<int>> d;

int dfs(int i, int p){
    int res = 0;
    for(auto x: d[i])
        if(x != p){
            res += dfs(x, i);
        }
    return res + 1;
}

int main()
{
    cin >> n;
    d.resize(n + 1);
    for(int i = 1; i < n; ++ i) {
        int x, y;
        cin >> x >> y;
        d[x].push_back(y);
        d[y].push_back(x);
    }

    int ret = 0;
    for(auto& x : d[1])
        ret = max(ret, dfs(x, 1));
    cout << ret << endl;

    return 0;
}