mirror of
https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
101 lines
2.5 KiB
C++
101 lines
2.5 KiB
C++
#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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#include <string.h>
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#include <string>
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#include <vector>
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#include <map>
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#include <set>
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#include <queue>
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#include <algorithm>
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#include <iostream>
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#include <sstream>
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using namespace std;
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const int maxn = 2505;
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struct Graph {
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int hed[maxn], pnt[maxn*2], val[maxn*2], nxt[maxn*2], cnt;
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void init(int n) {
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cnt = 0;
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memset(hed, -1, 4 * n);
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}
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void addedge(int x, int y, int v) {
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pnt[cnt] = y; val[cnt] = v; nxt[cnt] = hed[x]; hed[x] = cnt++;
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pnt[cnt] = x; val[cnt] = v; nxt[cnt] = hed[y]; hed[y] = cnt++;
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}
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} g;
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queue<int> Q;
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int n;
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int banx, bany;
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int par[maxn], dis[maxn];
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int xx, yy;
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int bfs(int x) {
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int ret = x;
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dis[x] = 0;
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Q.push(x);
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while (!Q.empty()) {
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int a = Q.front();
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Q.pop();
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for (int p = g.hed[a]; p != -1; p = g.nxt[p]) {
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int b = g.pnt[p];
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if (dis[b] != -1) continue;
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if (a == banx && b == bany || a == bany && b == banx) continue;
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par[b] = a;
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dis[b] = dis[a] + g.val[p];
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Q.push(b);
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if (dis[b] > dis[ret]) ret = b;
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}
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}
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return ret;
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}
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void FindRoad(int x) {
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memset(par, -1, 4 * n);
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memset(dis, -1, 4 * n);
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yy = bfs(x);
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memset(par, -1, 4 * n);
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memset(dis, -1, 4 * n);
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xx = bfs(yy);
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}
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int ans;
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vector<int> v, d;
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void Solve() {
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int t, disx, disy, disedge, dxx, dyy;
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banx = bany = -1;
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FindRoad(0);
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v.clear(); d.clear();
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t = xx;
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while (true) {
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v.push_back(t);
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t = par[t];
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if (t == -1) break;
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d.push_back(dis[v.back()] - dis[t]);
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}
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ans = dis[xx];
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for (int i = 1; i < v.size(); i++) {
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banx = v[i-1]; bany = v[i];
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disedge = d[i-1];
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FindRoad(banx);
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dxx = disx = dis[xx];
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for (t = xx; t != -1; t = par[t])
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disx = min(disx, max(dis[xx] - dis[t], dis[t]));
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FindRoad(bany);
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dyy = disy = dis[xx];
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for (t = xx; t != -1; t = par[t])
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disy = min(disy, max(dis[xx] - dis[t], dis[t]));
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ans = min(ans, max(max(disx + disy + disedge, dxx), dyy));
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}
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}
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int main() {
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int t, x, y, v, i, cas = 1;
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for (scanf("%d", &t); t--; ) {
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scanf("%d", &n);
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g.init(n);
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for (i = 1; i < n; i++) {
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scanf("%d %d %d", &x, &y, &v);
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g.addedge(x, y, v);
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}
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Solve();
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printf("Case %d: %d\n", cas++, ans);
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}
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return 0;
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}
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