HDU 4756 Install Air Conditioning

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 const int maxn = 1010;
18 double g[maxn][maxn],d[maxn],px[maxn],py[maxn],dp[maxn][maxn];
19 int p[maxn],n,m;
20 vector<int>e[maxn];
21 bool used[maxn][maxn];
22 double getDis(int i,int j) {
23     double tmp = (px[i] - px[j])*(px[i] - px[j]);
24     tmp += (py[i] - py[j])*(py[i] - py[j]);
25     return sqrt(tmp);
26 }
27 double prim() {
28     bool vis[maxn] = {false};
29     for(int i = 1; i <= n; ++i) {
30         d[i] = INF;
31         p[i] = -1;
32     }
33     d[1] = 0;
34     double MST = 0;
35     while(true) {
36         double minVal = INF;
37         int idx = -1;
38         for(int i = 1; i <= n; ++i)
39             if(!vis[i] && minVal > d[i]) minVal = d[idx = i];
40         if(idx == -1 || minVal >= INF) break;
41         if(p[idx] > -1) {
42             e[idx].push_back(p[idx]);
43             e[p[idx]].push_back(idx);
44             used[idx][p[idx]] = used[p[idx]][idx] = true;
45         }
46         vis[idx] = true;
47         MST += minVal;
48         for(int i = 1; i <= n; ++i)
49             if(!vis[i] && d[i] > g[idx][i]) {
50                 d[i] = g[idx][i];
51                 p[i] = idx;
52             }
53     }
54     return MST;
55 }
56 double dfs(int cur,int u,int fa){
57     double minV = INF;
58     for(int i = e[u].size()-1; i >= 0; --i){
59         if(e[u][i] == fa) continue;
60         double tmp = dfs(cur,e[u][i],u);
61         minV = min(tmp,minV);
62         dp[u][e[u][i]] = dp[e[u][i]][u] = min(tmp,dp[u][e[u][i]]);
63     }
64     if(cur != fa) minV = min(minV,g[cur][u]);
65     return minV;
66 }
67 int main() {
68     int cs;
69     scanf("%d",&cs);
70     while(cs--){
71         scanf("%d %d",&n,&m);
72         for(int i = 0; i <= n; ++i) e[i].clear();
73         for(int i = 1; i <= n; ++i)
74             scanf("%lf %lf",px+i,py+i);
75         for(int i = 1; i <= n; ++i){
76             for(int j = 1; j <= n; ++j){
77                 if(i == j) g[i][j] = 0;
78                 else g[i][j] = getDis(i,j);
79                 dp[i][j] = INF;
80             }
81         }
82         double MST = prim(),ans = MST;
83         for(int i = 1; i <= n; ++i) dfs(i,i,-1);
84         for(int i = 2; i <= n; ++i){
85             for(int j = e[i].size()-1; j >= 0; --j){
86                 if(e[i][j] == 1) continue;
87                 ans = max(ans,MST - g[i][e[i][j]] + dp[i][e[i][j]]);
88             }
89         }
90         printf("%.2f\n",ans*m);
91     }
92     return 0;
93 }