HDU4081 Qin Shi Huang's National Road System
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#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1100;
const int INF = 147483647;
bool vis[MAXN];
double lowc[MAXN];
int pre[MAXN];
double MAX[MAXN][MAXN];
bool used[MAXN][MAXN];
double x[1010], y[1010], people[1010];
double cost[MAXN][MAXN];
void init()
memset(lowc, 0, sizeof(lowc));
memset(pre, 0, sizeof(pre));
memset(cost, 0, sizeof(cost));
double Prim(int n)
double ans = 0;
memset(vis, false, sizeof(vis));
memset(MAX, 0, sizeof(MAX));
memset(used, false, sizeof(used));
vis[0] = true;
pre[0] = -1;
lowc[0] = 0;
for (int i = 1; i < n; i++)
lowc[i] = cost[0][i];
pre[i] = 0;
for (int i = 1; i < n; i++)
double minc = INF;
int p = -1;
for (int j = 0; j < n; j++)
if (!vis[j] && minc > lowc[j])
minc = lowc[j];
p = j;
if (minc == INF)
return -1;
ans += minc;
vis[p] = true;
used[p][pre[p]] = used[pre[p]][p] = true;
for (int j = 0; j < n; j++)
if (vis[j]&&j!=p) //这里加上j!=p就AC了,目前原因未知
MAX[j][p] = MAX[p][j] = max(MAX[j][pre[p]], lowc[p]);
if (!vis[j] && lowc[j] > cost[p][j])
lowc[j] = cost[p][j];
pre[j] = p;
return ans;
double dist(double xa, double ya, double xb, double yb)
return sqrt((xa - xb) * (xa - xb) + (ya - yb) * (ya - yb));
int main()
int _, n;
scanf("%d", &_);
while (_--)
scanf("%d", &n);
init();
for (int i = 0; i < n; i++)
scanf("%lf %lf %lf", &x[i], &y[i], &people[i]);
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
cost[i][j] = cost[j][i] = dist(x[i], y[i], x[j], y[j]);
double sum = Prim(n), ans = -1;
// cout << sum << endl;
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
if (i == j) continue;
if (!used[i][j])
ans = max(ans, (people[i] + people[j]) / (sum - MAX[i][j]));
else
ans = max(ans, (people[i] + people[j]) / (sum - cost[i][j]));
printf("%.2f\n", ans);
return 0;
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