Jungle Roads
Time Limit : 2000/1000ms (Java/Other) Memory Limit : 65536/32768K (Java/Other)
Total Submission(s) : 45 Accepted Submission(s) : 34
Problem Description
The Head Elder of the tropical island of Lagrishan has a problem. A burst of foreign aid money was spent on extra roads between villages some years ago. But the jungle overtakes roads relentlessly, so the large road network is too expensive to maintain. The Council of Elders must choose to stop maintaining some roads. The map above on the left shows all the roads in use now and the cost in aacms per month to maintain them. Of course there needs to be some way to get between all the villages on maintained roads, even if the route is not as short as before. The Chief Elder would like to tell the Council of Elders what would be the smallest amount they could spend in aacms per month to maintain roads that would connect all the villages. The villages are labeled A through I in the maps above. The map on the right shows the roads that could be maintained most cheaply, for 216 aacms per month. Your task is to write a program that will solve such problems.
The input consists of one to 100 data sets, followed by a final line containing only 0. Each data set starts with a line containing only a number n, which is the number of villages, 1 < n < 27, and the villages are labeled with the first n letters of the alphabet, capitalized. Each data set is completed with n-1 lines that start with village labels in alphabetical order. There is no line for the last village. Each line for a village starts with the village label followed by a number, k, of roads from this village to villages with labels later in the alphabet. If k is greater than 0, the line continues with data for each of the k roads. The data for each road is the village label for the other end of the road followed by the monthly maintenance cost in aacms for the road. Maintenance costs will be positive integers less than 100. All data fields in the row are separated by single blanks. The road network will always allow travel between all the villages. The network will never have more than 75 roads. No village will have more than 15 roads going to other villages (before or after in the alphabet). In the sample input below, the first data set goes with the map above.
The output is one integer per line for each data set: the minimum cost in aacms per month to maintain a road system that connect all the villages. Caution: A brute force solution that examines every possible set of roads will not finish within the one minute time limit.
Sample Input
9
A 2 B 12 I 25
B 3 C 10 H 40 I 8
C 2 D 18 G 55
D 1 E 44
E 2 F 60 G 38
F 0
G 1 H 35
H 1 I 35
3
A 2 B 10 C 40
B 1 C 20
0
Sample Output
216
30
題意：
首先輸入一個數n，代表村莊的個數，然後輸入n-1行，每一行第一個字母代表一個村莊，然後後面那個數代表要連的村莊的個數，然後輸入要連的村莊和對應的距離，輸入0代表輸入結束！讓求最短的距離能將各個村莊都聯系起來！
思路：
從邊的角度出發進行考慮，題目離散的將點和距離都告訴了我們，我們就要將他們都建立一個聯系（通過結構體），然後把邊都建立起來之後，就只剩下用最小生成樹的方法求解就行了！
代碼：
#include #include #include #include using namespace std; int n,m; char pre[105];//注意這是字符型的，就這一點最容易出錯！ void init() { for(char i='A';i<='Z';i++) pre[i]=i; } struct node { int u,v,w; }p[10005]; int find(int x)//找根節點 { int r=x; while(r!=pre[r]) { r=pre[r]; } int i,j; i=x; while(i!=r) { j=pre[i]; pre[i]=r; i=j; } return r; } int join(int x,int y)//連到一起 { int fx=find(x); int fy=find(y); if(fx!=fy)//判斷是否成環！ { pre[fx]=fy; return 1; } return 0; } int cmp(node a,node b) { return a.w
