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41 lines
1.0 KiB
41 lines
1.0 KiB
#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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// 暴力搜索，从每个节点为根出发，遍历整根树，找出距离自己的最大距离,然后每个最大距离取min
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// 11/17,其它TLE,无法AC
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int n;
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int ans; // 树的直径
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// 邻接表
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int e[M], h[N], idx, w[M], ne[M];
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void add(int a, int b, int c = 0) {
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e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
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}
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void dfs(int u, int fa, int sum) {
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if (sum > ans) ans = sum;
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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; // 不走回头路
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dfs(v, u, sum + w[i]);
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}
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}
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int main() {
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// 初始化邻接表
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memset(h, -1, sizeof h);
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cin >> n;
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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); // 无向图
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}
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// 多次dfs,是TLE的罪魁祸首
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for (int i = 1; i <= n; i++) dfs(i, 0, 0);
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// 输出结果
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printf("%d", ans);
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return 0;
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} |