公路修建

Posted 2020-09-12 蒟蒻zht的博客

洛谷传送门

这道水题告诉了我，堆优化的prim有时还不如朴素prim快。。。

居然记错时间复杂度了，我也真是菜。

 1 #include <cstdio>
 2 #include <queue>
 3 #include <cmath>
 4 
 5 using namespace std;
 6 
 7 int n;
 8 double ans, map[5001][2], minn[5001];
 9 bool vis[5001];
10 
11 inline double dis(int x, int y)
12 {
13     return sqrt((map[x][0] - map[y][0]) * (map[x][0] - map[y][0]) + (map[x][1] - map[y][1]) * (map[x][1] - map[y][1]));
14 }
15 
16 inline void queue_prim()
17 {
18     int i, j, k;
19     double l;
20     for(i = 0; i <= n; i++) minn[i] = 99999999;
21     minn[1] = 0;
22     for(i = 1; i <= n; i++)
23     {
24         k = 0;
25         for(j = 1; j <= n; j++)
26          if(!vis[j] && minn[j] < minn[k])
27           k = j;
28         vis[k] = 1;
29         for(j = 1; j <= n; j++)
30         {
31             l = dis(k, j);
32             if(!vis[j] && l < minn[j]) minn[j] = l;
33         }
34     }
35     for(i = 1; i <= n; i++) ans += minn[i];
36 }
37 
38 int main()
39 {
40     int i;
41     scanf("%d", &n);
42     for(i = 1; i <= n; i++) scanf("%lf %lf", &map[i][0], &map[i][1]);
43     queue_prim();
44     printf("%.2lf", ans);
45     return 0;
46 }

View Code