#include<iostream>
using namespace std;
char a[23][23];
int large=0;
void DFS(int i,int j,int counter,bool c[],bool visit[][23])
{
    if(!c[a[i][j]-'A'+1])
        c[a[i][j]-'A'+1]=true;
    if(counter>large)
        large=counter;  
    if(counter>large)
           large=counter;
    if(!visit[i+1][j] && !c[a[i+1][j]-'A'+1] && a[i+1][j]>='A' && a[i+1][j]<='Z')
           DFS(i+1,j,counter+1,c,visit);
    if(!visit[i-1][j] && !c[a[i-1][j]-'A'+1] && a[i-1][j]>='A' && a[i-1][j]<='Z')
           DFS(i-1,j,counter+1,c,visit);
    if(!visit[i][j+1] && !c[a[i][j+1]-'A'+1] && a[i][j+1]>='A' && a[i][j+1]<='Z')
           DFS(i,j+1,counter+1,c,visit);
    if(!visit[i][j-1] && !c[a[i][j-1]-'A'+1] && a[i][j-1]>='A' && a[i][j-1]<='Z')
           DFS(i,j-1,counter+1,c,visit);
    return;
}           
int main()
{
    int r,s;
    bool visit[23][23];
    bool c[27];
    memset(c,false,sizeof(c));
    
    scanf("%d %d",&r,&s);
    while(getchar()!='\n');
    for(int i=0;i<=21;i++)
            for(int j=0;j<=21;j++)
            {
                    a[i][j]=0;
                    visit[i][j]=true;
            }//init
    for(int i=1;i<=r;i++)
    {
            for(int j=1;j<=s;j++)
            {
                    scanf("%c",&a[i][j]);
                    visit[i][j]=false;
            }
            while(getchar()!='\n');
    }
    DFS(1,1,1,c,visit);
    printf("%d\n",large);
    system("pause");
    return 0;
}

• forget backtrack？ (1578) lxc0601 2008-05-15 19:50:50