HDU 1181 变形课

题目链接http://acm.hdu.edu.cn/showproblem.php?pid=1181

此题多种方法。比如说Flyod传递闭包 就能搞定 这里只写DFS和BFS

熟悉下。只有DFS是我写的，其他的都是同学的。

DFS

View Code

 1 #include <stdio.h>

 2 #include <string.h>

 3 #include <stdlib.h>

 4 #define N 30

 5 int m[N][N],flag,visit[N];

 6 void dfs(int n)

 7 {

 8     int i;

 9     if(n=='m'-'a')

10     {

11         flag=1;return;

12     }

13     for(i=0;i<26;i++)

14     {

15        if(m[n][i]==1&&!visit[i])

16        {

17            visit[i]=1;

18            dfs(i);

19        }

20     }

21 }

22 int main()

23 {

24     char s[100];int len;

25     memset(m,0,sizeof(m));

26     memset(visit,0,sizeof(visit));

27     while(scanf("%s",s)&&s[0]!='0')

28     {

29         len=strlen(s);

30         m[s[0]-'a'][s[len-1]-'a']=1;

31         while(scanf("%s",s)&&s[0]!='0')

32         {

33             flag=0;

34             len=strlen(s);

35             m[s[0]-'a'][s[len-1]-'a']=1;

36         }

37         dfs(1);

38         flag== 1 ? printf( "Yes.\n" ) : printf( "No.\n" );

39     }

40     return 0;

41 }

BFS

View Code

 1 #include<stdio.h>

 2 #include<string.h>

 3 int q[100000];

 4 int map[30][30];

 5 int pro[100000];

 6 int f,r;

 7 

 8 int main()

 9 {

10     int n,i,j,len,leap;

11     char s[200];

12     while(scanf("%s",s) != EOF)

13     {

14         leap = 0;

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

16         memset(pro,0,sizeof(pro));

17         memset(q,0,sizeof(q));

18         len = strlen(s);

19         map[s[0]-'a'][s[len-1]-'a'] = 1;

20 

21         while(scanf("%s",s) != EOF)

22         {

23             len = strlen(s);

24             if(s[0] == '0')

25             break;

26             map[s[0]-'a'][s[len-1]-'a'] = 1;

27         }

28         f = 0,r = 0;

29         q[r++] = 'b'-'a';

30         while(f < r)

31         {

32             int v;

33             v = q[f++];

34             for(i = 0;i < 26;i++)

35             {

36                 if(map[v][i] && !pro[i])

37                 {

38                     if(i == 'm'-'a')

39                     {

40                         leap = 1;

41                         break;

42                     }

43                     q[r++] = i;

44                     pro[i] = 1;

45                 }

46             }

47             if(leap)

48             break;

49         }

50         if(leap)

51         puts("Yes.");

52         else

53         puts("No.");

54     }

55     return 0;

56 }

用STL queue实现队列的 BFS

View Code

 1 #include <queue> 

 2 #include <cstdio> 

 3 #include <cstring> 

 4 #include <iostream> 

 5 using namespace std; 

 6 

 7 const int N=1001; 

 8 int map[N][N]; 

 9 int vis[N]; 

10 queue<int>q; 

11 

12 int bfs() 

13 { 

14     while(!q.empty()) 

15     { 

16         int a; 

17         a=q.front(); 

18         q.pop(); 

19         for(int i=0;i<26;i++) 

20         { 

21             if(map[a][i]&&!vis[i]) 

22             { 

23                 if(i=='m'-'a') 

24                 { 

25                     return 1; 

26                 } 

27                 q.push(i); 

28                 vis[i]=1; 

29             } 

30         } 

31     } 

32     return 0; 

33 } 

34 

35 int main() 

36 { 

37     int len; 

38     char s[N]; 

39     while(~scanf("%s",s)) 

40     { 

41         while(!q.empty()) 

42             q.pop(); 

43         memset(map,0,sizeof(map)); 

44         memset(vis,0,sizeof(vis)); 

45         len=strlen(s); 

46         map[s[0]-'a'][s[len-1]-'a']=1; 

47         while(~scanf("%s",s)) 

48         { 

49             len=strlen(s); 

50             if(s[0]=='0') 

51                 break; 

52             map[s[0]-'a'][s[len-1]-'a']=1; 

53         } 

54         q.push('b'-'a'); 

55         if(bfs()) 

56             puts("Yes."); 

57         else 

58             puts("No."); 

59     } 

60     return 0; 

61 }