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#include <bits/stdc++.h>
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using namespace std;
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const int N = 10010, M = N << 1;
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int n; // n个结点
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// 链式前向星
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int h[N], e[M], w[M], ne[M], idx;
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void add(int a, int b, int c) {
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e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx++;
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}
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int ans; // 答案,直径
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int mx1[N], mx2[N]; // mx1[i],mx2[i]:经过i点的最长,次长长度是多少
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void dfs(int u, int fa) {
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for (int i = h[u]; ~i; i = ne[i]) {
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int v = e[i];
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if (v == fa) continue; // v点访问过了
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// 走v子树,完成后，v子树中每个节点的mx1[v],mx2[v]都已经准备好，u节点可以直接利用
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dfs(v, u);
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// w[i]:u->v的路径长度,mx1[u]:最长路径,mx2[u]:次长路径
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int x = mx1[v] + w[i];
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if (mx1[u] <= x) // v可以用来更新u的最大值
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mx2[u] = mx1[u], mx1[u] = x; // 最长路转移
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else if (mx2[u] < x)
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mx2[u] = x; // 次长路转移
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}
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// 更新结果
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ans = max(ans, mx1[u] + mx2[u]);
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}
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int main() {
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cin >> n;
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memset(h, -1, sizeof h); // 初始化邻接表
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for (int i = 1; i < n; i++) { // n-1条边
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int a, b, c;
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cin >> a >> b >> c;
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add(a, b, c), add(b, a, c); // 换根dp一般用于无向图
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}
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dfs(1, 0); // 任选一个点作为根节点,此处选择的是肯定存在的1号结点
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cout << ans << endl;
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return 0;
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}
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