poj 3164 Command Network

　　继续最小树形图~

　　这次的最小树形图直接套模板上去就可以了....我把刚才那篇的写法用上去，AC的还是相当顺利的，就只有刚开始打错了几个字，搞到TLE了一下。于是，我确定这种写法（我觉得已经是相当飘逸的了）可以加入我的模板...

　　题意就没必要解释了，这么明显。

View Code

  1 #include <cstdio>
  2 #include <cstring>
  3 #include <cstdlib>
  4 #include <cmath>
  5 
  6 typedef double ll;
  7 
  8 const int maxn = 105;
  9 const ll inf = 1e30;
 10 int pre[maxn], fold[maxn], vis[maxn];
 11 ll cost[maxn], min_cost;
 12 
 13 struct edge{
 14     int b;
 15     int e;
 16     ll c;
 17 }E[maxn * maxn];
 18 
 19 struct point{
 20     ll x;
 21     ll y;
 22 }P[maxn];
 23 
 24 ll dis(point a, point b){
 25     ll dx = a.x - b.x;
 26     ll dy = a.y - b.y;
 27 
 28     return sqrt(dx * dx + dy * dy);
 29 }
 30 
 31 bool make_tree(int root, int v, int e){
 32     int i, j;
 33     int s, t, cnt;
 34 
 35     min_cost = 0;
 36     while (true){
 37         for (i = 0; i < v; i++){
 38             cost[i] = 1e31;
 39         }
 40         for (i = 0; i < e; i++){
 41             s = E[i].b;
 42             t = E[i].e;
 43             #ifndef ONLINE_JUDGE
 44             printf("%d %d: %.2f\n", s, t, E[i].c);
 45             #endif
 46 
 47             if (cost[t] > E[i].c && s != t){
 48                 cost[t] = E[i].c;
 49                 pre[t] = s;
 50             }
 51         }
 52         #ifndef ONLINE_JUDGE
 53         for (i = 0; i < v; i++)
 54             printf("%d  pre : %d   in : %.2f\n", i, pre[i], cost[i]);
 55         puts("");
 56         #endif
 57         cost[root] = 0;
 58         for (i = 0; i < v; i++){
 59             min_cost += cost[i];
 60             fold[i] = vis[i] = -1;
 61             if (cost[i] > inf && i != root) return false;
 62         }
 63 
 64         cnt = 0;
 65         for (i = 0; i < v; i++){
 66             j = i;
 67             vis[i] = i;
 68             for (j = pre[j]; j != root && vis[j] != i && fold[i] == -1; j = pre[j]) vis[j] = i;
 69             if (j == root || fold[j] != -1) continue;
 70             for (s = j, fold[s] = cnt, s = pre[s]; s != j; s = pre[s]) fold[s] = cnt;
 71             cnt++;
 72         }
 73         if (!cnt) return true;
 74         for (i = 0; i < v; i++){
 75             if (fold[i] == -1) fold[i] = cnt++;
 76         }
 77         #ifndef ONLINE_JUDGE
 78         for (i = 0; i < v; i++) printf("fold %d : %d\n", i, fold[i]);
 79         #endif
 80         for (i = 0; i < e; i++){
 81             s = E[i].b;
 82             t = E[i].e;
 83 
 84             E[i].b = fold[s];
 85             E[i].e = fold[t];
 86             if (E[i].b != E[i].e){
 87                 E[i].c -= cost[t];
 88             }
 89         }
 90         v = cnt;
 91         root = fold[root];
 92     }
 93 }
 94 
 95 
 96 bool deal(){
 97     int n, m;
 98     int b, e;
 99 
100     if (scanf("%d%d", &n, &m) == EOF) return false;
101     for (int i = 0; i < n; i++){
102         scanf("%lf%lf", &P[i].x, &P[i].y);
103     }
104     for (int i = 0; i < m; i++){
105         scanf("%d%d", &b, &e);
106         b--; e--;
107         E[i].b = b;
108         E[i].e = e;
109         E[i].c = dis(P[b], P[e]); // coordinate transform
110     }
111     if (make_tree(0, n, m)){
112         printf("%.2f\n", min_cost);
113     }
114     else puts("poor snoopy");
115 
116     return true;
117 }
118 
119 int main(){
120     #ifndef ONLINE_JUDGE
121     freopen("in", "r", stdin);
122     #endif
123     while (deal());
124 
125     return 0;
126 }

——written by Lyon

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原文地址：https://www.cnblogs.com/LyonLys/p/poj_3164_Lyon.html