OJ-Problems-Source/HDOJ/3721_autoAC.cpp

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