杭电2122--Ice_cream's world III-优快云博客

本文介绍了一个基于最小生成树算法的编程问题——冰激凌世界III，通过并查集实现克鲁斯卡尔算法来寻找最优路径，确保每个城市到首都的连接成本最低。如果无法满足条件，则输出'impossible'。

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Ice_cream’s world III

Time Limit: 3000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1146 Accepted Submission(s): 379

Problem Description

ice_cream’s world becomes stronger and stronger; every road is built as undirected. The queen enjoys traveling around her world; the queen’s requirement is like II problem, beautifies the roads, by which there are some ways from every city to the capital. The project’s cost should be as less as better.

Input

Every case have two integers N and M (N<=1000, M<=10000) meaning N cities and M roads, the cities numbered 0…N-1, following N lines, each line contain three integers S, T and C, meaning S connected with T have a road will cost C.

Output

If Wiskey can’t satisfy the queen’s requirement, you must be output “impossible”, otherwise, print the minimum cost in this project. After every case print one blank.

Sample Input

2 1

     0 1 10 
   

4 0

Sample Output

10

     impossible 
   

Author

Wiskey

Source

HDU 2007-10 Programming Contest_WarmUp

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//并查集实现克鲁斯卡尔；

 1 #include <stdio.h>
 2 #include <algorithm>
 3 using namespace std;
 4 int father[1010] ;
 5 
 6 struct rode
 7 {
 8     int a, b ,c;
 9 };
10 rode num[10010];
11 
12 bool cmp(rode a, rode b)
13 {
14     return a.c < b.c ;
15 }
16 
17 int find(int a)
18 {
19     while(a != father[a])
20     a = father[a];
21     return a;
22 }
23 
24 void mercy(int a, int b)
25 {
26     int q = find(a);
27     int p = find(b);
28     if(q != p)
29     father[q] = p;
30         
31 }
32 
33 int main()
34 {
35     int i, n, m;
36     while(~scanf("%d %d", &n, &m))
37     {
38         for(i=0; i<n; i++)
39         father[i] = i;
40         for(i=0; i<m; i++)
41         scanf("%d %d %d",&num[i].a, &num[i].b, &num[i].c);
42         sort(num, num+m, cmp);
43         int total = 0;
44         for(i=0; i<m; i++)
45         {
46             //mercy(num[i].a, num[i].b);
47             if(find(num[i].a) == find(num[i].b))
48             continue;
49             else
50             {
51                 //printf("1\n");
52                 total += num[i].c;
53                 mercy(num[i].a, num[i].b) ;
54             }    
55         }
56         int ac = 0;
57         for(i=0; i<n; i++)
58         {
59             if(father[i] == i)
60             ac++;
61         }
62         if(ac == 1)
63         printf("%d\n\n", total);
64         else
65         printf("impossible\n\n");
66     }
67 }