1930. Ivan's Car（ｓｐｆａ）

１９３０

简单二维　标记一下是上坡还是下坡

 1 #include <iostream>

 2 #include<cstdio>

 3 #include<cstring>

 4 #include<algorithm>

 5 #include<stdlib.h>

 6 #include<vector>

 7 #include<queue>

 8 using namespace std;

 9 #define N 10010

10 #define INF 0xfffffff

11 int dis[N][2],vis[N];

12 int n;

13 struct node

14 {

15     int u,v,next,d;

16 }ed[N*20];

17 int t,head[N];

18 void init()

19 {

20     t = 0;

21     memset(head,-1,sizeof(head));

22 }

23 void add(int u,int v,int d)

24 {

25     ed[t].u = u;

26     ed[t].v = v;

27     ed[t].d = d;

28     ed[t].next = head[u];

29     head[u] = t++;

30 }

31 int spfa(int s,int e)

32 {

33     int i;

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

35     {

36         dis[i][0] = INF;

37         dis[i][1] = INF;

38     }

39     dis[s][0] = 0;

40     dis[s][1] = 0;

41     queue<int>q;

42     q.push(s);

43     vis[s] = 1;

44     while(!q.empty())

45     {

46         int u = q.front();

47         q.pop();

48         for(i = head[u] ; i != -1 ; i = ed[i].next)

49         {

50             int v = ed[i].v;

51             int d = ed[i].d;

52             if(d)

53             dis[v][1] = min(min(dis[u][1],dis[u][0]+1),dis[v][1]);

54             else

55             dis[v][0] = min(min(dis[u][0],dis[u][1]+1),dis[v][0]);

56             if(!vis[v])

57             {

58                 vis[v] =  1;

59                 q.push(v);

60             }

61         }

62     }

63     return min(dis[e][1],dis[e][0]);

64 }

65 int main()

66 {

67     int i,u,v,m;

68     init();

69     scanf("%d%d",&n,&m);

70     for(i = 1; i <= m ;i++)

71     {

72         scanf("%d%d",&u,&v);

73         add(u,v,1);

74         add(v,u,0);

75     }

76     int s,e;

77     scanf("%d%d",&s,&e);

78     printf("%d\n",spfa(s,e));

79     return 0;

80 }

View Code