hdu 1181 变形课 （bfs）

 

 

#include<cstdio>

#include<cstring>

#include<cmath>

#include<algorithm>

#include<iostream>

#include<queue>

using namespace std;

char str[100];

int mat[30][30];

int vis[30][30];

int ok;

bool isok(int now,int next)

{

    if(mat[now][next]==0||vis[now][next]==1) return false;

    return true;

}

void bfs()

{

    int i,j,k;

    queue<int> q;

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

    while(!q.empty())

    {

       int now,next;

       now=q.front();

       q.pop();

       if(now=='m'-'a')

       {

           ok=1;

           return ;

       }

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

       {

           next=i;

           if(isok(now,next))

           {

               if(now=='m'-'a')

               {

                 ok=1;

                 return ;

               }

               vis[now][next]=1;

               q.push(next);

           }

       }



    }

}



int main()

{

    int cnt;

    int n;

    int i,j,k;

    int f,t;

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

    {

        if(strcmp(str,"0")==0)

        {

            printf("No.\n");continue;

        }

        ok=0;

        memset(mat,0,sizeof(mat));

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

        f=str[0]-'a';

        t=str[strlen(str)-1]-'a';

        mat[f][t]=1;

        while(1)

        {

            scanf("%s",str);

            if(strcmp(str,"0")==0) break;

            f=str[0]-'a';

            t=str[strlen(str)-1]-'a';

            mat[f][t]=1;

        }

        bfs();

        if(ok) printf("Yes.\n");

        else printf("No.\n");

    }

    return 0;

}