poj2377

http://poj.org/problem?id=2377

题意为给你一幅图，让你判断图有无最大支撑树，若有则求解图的最大支撑树，若无则输出-1

由于题目给的数据方式用kruskal比较方便，然后我们用已采纳的边数来断定图是否连通，边数=节点数-1

1 #include < stdio.h >
2 #include < algorithm >
3   using namespace std;
4 struct line
5 {
6 int begin;
7 int end;
8 int lenth;
9 };
10 line * amount;
11 int * father;
12 int numofnode,numofline;
13 int i,j,a,b,c;
14 int minlen;
15 int find( int k)
16 {
17 return father[k] == k ? k:father[k] = find(father[k]);
18 }
19 int cmp(line a,line b)
20 {
21 return a.lenth > b.lenth ? 1 : 0 ;
22 }
23 void ini()
24 {
25 scanf( " %d %d " , & numofnode, & numofline);
26 father = new int [numofline + 1 ];
27 amount = new line [numofline];
28 for (i = 1 ;i <= numofnode;i ++ ) father[i] = i;
29 for (i = 0 ;i < numofline;i ++ )
30 {
31 scanf( " %d %d %d " , & a, & b, & c);
32 amount[i].begin = a;
33 amount[i].end = b;
34 amount[i].lenth = c;
35 }
36 sort(amount,amount + numofline,cmp);
37 }
38 int kruskal()
39 {
40 minlen = 0 ;
41 int counter = 0 ;
42 for (i = 0 ;i < numofline;i ++ )
43 {
44 a = find(amount[i].begin),b = find(amount[i].end);
45 if (a != b)
46 {
47 father[a] = b;
48 minlen += amount[i].lenth;
49 counter ++ ;
50 }
51 }
52 return counter;
53 }
54 void pr()
55 {
56 int k = kruskal();
57 if (k < numofnode - 1 ) printf( " -1\n " );
58 else printf( " %d\n " ,minlen);
59 delete [] father;
60 delete [] amount;
61 }
62 int main()
63 {
64 ini();
65 pr();
66 return 0 ;
67 }

转载于:https://www.cnblogs.com/mengxm-lincf/archive/2011/06/06/2073451.html