TLE: HDOJ 1010 Tempter of the Bone

超时了，dfs写的是对的（通过了discuss中一块强大的数据）

谁说TLE的代码没有用？

# include <stdio.h>

# include <string.h>





typedef struct{

    int x, y;

}Point;



const Point d[4] = {{-1,0}, {0,1}, {0,-1}, {1,0}};



int N, M, T, tot, ok;

char m[8][8];



int dfs(Point s, int dir);

int can_move(Point s, int dir);

void solve(Point s, Point e, int T);



int main()

{

    int i;

    char *p;

    Point s, e;

    

    freopen("in.txt", "r", stdin);

    freopen("out.txt", "w", stdout);

    

    while (1)

    {

        scanf("%d%d%d", &N, &M, &T);

        if (!N && !M && !T) break;

        

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

        

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

        {

            scanf("%s", m[i]+1);

            if ((p = strchr(m[i]+1, 'S')) != NULL) {s.x = i; s.y = p-m[i];}

             if ((p = strchr(m[i]+1, 'D')) != NULL) {e.x = i; e.y = p-m[i];}

           }

           

           solve(s, e, T);

    }

    

    return 0;

}





int dfs(Point s, int dir)

{

    int ddir, f;

    

    f = 0;

    ++tot;

    s.x = s.x + d[dir].x;

    s.y = s.y + d[dir].y;

    if (m[s.x][s.y] == 'D') f = 1;

    if (tot == T && f) return ok = 1;

    m[s.x][s.y] = 'L';

    for ( ddir = 0; ddir < 4; ++ddir)

    {

         if (ddir != 3-dir && can_move(s, ddir))

            dfs(s, ddir);

    }

    --tot;

    if (!f)m[s.x][s.y] = '.';

    else m[s.x][s.y] = 'D';

}



int can_move(Point s, int dir)

{

    Point nx; 

    nx.x = s.x + d[dir].x;

    nx.y = s.y + d[dir].y;

    if (1 <= nx.x && nx.x <= N && 1 <= nx.y && nx.y <= M && (m[nx.x][nx.y] == '.' || m[nx.x][nx.y] == 'D'))

        return 1;       

       return 0;

}



void solve(Point s, Point e, int T)

{

    int dir;

    

    if (T >= N*M) {printf("NO\n"); return ;}

    if (m[s.x][s.y] == 'D')

    {

        if (T == 0) printf("YES\n");

        else printf("NO\n");

        return ;

    }

    m[s.x][s.y] = 'L';

    for (ok = dir = 0; dir < 4; ++dir)

    {

           tot = 0;

        if (can_move(s, dir) && !ok)

        {

            dfs(s, dir);

        }

    }

    printf(ok==1 ? "YES\n":"NO\n");

}