SDUT图结构练习——最小生成树

http://acm.sdut.edu.cn/sdutoj/showproblem.php?pid=2144&cid=1186

这道题一开始是用prim算法做的，一直错一直错，后来问了帅郭改用Kruskal做才对，再后来问了ＴＨＨ和二货才改对的prim算法，是因为重边我没处理啊，上火

 1 #include <cstdio>

 2 #include <cstring>

 3 #include<cstdlib>

 4 #include<iostream>

 5 using namespace std ;

 6 #define oo (1<<28)

 7 const int N = 110 ;

 8 int map[N][N],low[N],flag[N];//low数组是用来保留最小代价的；

 9 //flag数组是用来标记的，找过得点就不再去找

10 int m,n;

11 int u,v,w ;

12 int prim()

13 {

14     int i,j,pos,min,ans=0;

15     memset(flag,0,sizeof(flag));

16     flag[1]=1;

17     pos=1;

18     for(i = 1 ; i <= n ; i++)

19         if(i != pos)

20             low[i] = map[pos][i];

21     for(i = 1 ; i < n ; i++)

22     {

23         min=oo;

24         for(j = 1 ; j <= n ; j++)

25             if(flag[j] == 0&&min>=low[j])

26             {

27                 min = low[j];

28                 pos = j ;

29             }

30         ans += min ;

31         flag[pos] = 1 ;

32         for(j = 1 ; j <= n ; j++)

33             if(flag[j] == 0&&low[j]>map[pos][j])

34                 low[j]=map[pos][j];

35     }

36     return ans;

37 }

38 int main()

39 {

40     int ans;

41     while(scanf("%d %d",&n,&m)!=EOF)

42     {

43         for(int i = 1 ; i < N ; i++)

44         {

45             for(int j = 1 ; j < N ; j++)

46             {

47                 map[i][j] = oo ;

48             }

49         }

50         for(int i = 1 ; i <= m ; i++)

51         {

52             scanf("%d %d %d",&u,&v,&w);

53            if(map[u][v] >w)//防止重边出现保留小的重边

54             map[u][v] = map[v][u] = w ;

55         }

56         ans = prim();

57         printf("%d\n",ans);

58     }

59     return 0;

60 }

View Code

 1 #include<cstdio>

 2 #include<cstring>

 3 #include<cstdlib>

 4 #include<iostream>

 5 using namespace std ;

 6 const int MAXN = 10000 ;

 7 const int MAX = 100 ;

 8 int EDG[MAX];

 9 int sum;

10 struct node

11 {

12     int u ;

13     int v ;

14     int w ;

15 } map[MAXN],t;

16 int find(int x)

17 {

18     while(x!=EDG[x]){

19         x=EDG[x];

20     }

21     return x;

22 }

23 void Kruskal(int x,int y,int z)

24 {

25     x = find(x) ;

26     y = find(y) ;

27     if(x != y)

28     {

29         EDG[x] = y ;

30         sum += z;

31     }

32 }

33 int main()

34 {

35     int n,m,i,j;

36     while(~scanf("%d %d",&n,&m))

37     {

38         sum = 0 ;

39         int k = 0 ;

40         for(int i = 1 ; i <= n ; i++)

41             EDG[i] = i ;

42         for(int i = 1 ; i <= m ; i++)

43             scanf("%d %d %d",&map[i].u,&map[i].v,&map[i].w);

44         for(int i = 1 ; i <= m-1 ; i++){

45             for(j = i+1 ; j <= m ; j++){

46                 if(map[i].w > map[j].w)

47                 {

48                     t = map[i] ;

49                     map[i] = map[j];

50                     map[j] = t ;

51                 }

52             }

53         }

54         for(int i = 1 ; i <= m ; i++)

55             Kruskal(map[i].u,map[i].v,map[i].w);

56             printf("%d\n",sum);

57     }

58     return 0;

59 }

View Code