【SPOJ-ABCPATH】ABC Path【BFS/DFS】
题意：
n×m的格子，每个格子有一个大写英文字母，每个格子可以沿着八个方向走。问图中最长的从A开始的字母序列（ABCD...）的长度是多少。
搜索...
注意写vis标记，否则容易炸。
可以试试这组数据：
50 50 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA ABBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBA ABCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCBA ABCDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDCBA ABCDEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEDCBA ABCDEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEDCBA ABCDEFGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGFEDCBA ABCDEFGHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHGFEDCBA ABCDEFGHIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIHGFEDCBA ABCDEFGHIJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJIHGFEDCBA ABCDEFGHIJKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKJIHGFEDCBA ABCDEFGHIJKLLLLLLLLLLLLLLLLLLLLLLLLLLLLKJIHGFEDCBA ABCDEFGHIJKLMMMMMMMMMMMMMMMMMMMMMMMMMMLKJIHGFEDCBA ABCDEFGHIJKLMNNNNNNNNNNNNNNNNNNNNNNNNMLKJIHGFEDCBA ABCDEFGHIJKLMNOOOOOOOOOOOOOOOOOOOOOONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPPPPPPPPPPPPPPPPPPPPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQQQQQQQQQQQQQQQQQQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRRRRRRRRRRRRRRRRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSSSSSSSSSSSSSSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTTTTTTTTTTTTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUUUUUUUUUUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVVVVVVVVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWWWWWWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWXXXXWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWXYYXWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWXYYXWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWXXXXWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVWWWWWWVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUVVVVVVVVUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTUUUUUUUUUUTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSTTTTTTTTTTTTSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRSSSSSSSSSSSSSSRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQRRRRRRRRRRRRRRRRQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPQQQQQQQQQQQQQQQQQQPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOPPPPPPPPPPPPPPPPPPPPONMLKJIHGFEDCBA ABCDEFGHIJKLMNOOOOOOOOOOOOOOOOOOOOOONMLKJIHGFEDCBA ABCDEFGHIJKLMNNNNNNNNNNNNNNNNNNNNNNNNMLKJIHGFEDCBA ABCDEFGHIJKLMMMMMMMMMMMMMMMMMMMMMMMMMMLKJIHGFEDCBA ABCDEFGHIJKLLLLLLLLLLLLLLLLLLLLLLLLLLLLKJIHGFEDCBA ABCDEFGHIJKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKJIHGFEDCBA ABCDEFGHIJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJIHGFEDCBA ABCDEFGHIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIHGFEDCBA ABCDEFGHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHGFEDCBA ABCDEFGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGFEDCBA ABCDEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEDCBA ABCDEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEDCBA ABCDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDCBA ABCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCBA ABBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
#include <cstdio>
#include <algorithm>
using namespace std;
const int maxn = 55, maxq = 10000;
int n, m, g[maxn][maxn], vis[maxn][maxn];
int dx[] = {-1, -1, 0, 1, 1, 1, 0, -1};
int dy[] = {0, -1, -1, -1, 0, 1, 1, 1};
struct _point {
int x, y;
} q[maxq];
inline int iread() {
int f = 1, x = 0; char ch = getchar();
for(; ch < '0' || ch > '9'; ch = getchar()) f = ch == '-' ? -1 : 1;
for(; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';
return f * x;
}
int ans, clo;
inline void bfs(int sx, int sy) {
int h = 0, t = 0;
q[t++] = (_point) {sx, sy};
vis[sx][sy] = clo;
while(h != t) {
_point u = q[h++];
ans = max(ans, g[u.x][u.y]);
for(int i = 0; i < 8; i++) {
int x = u.x + dx[i], y = u.y + dy[i];
if(x >= 1 && x <= n && y >= 1 && y <= m) if((g[x][y] == g[u.x][u.y] + 1) && (vis[x][y] != clo))
vis[x][y] = clo, q[t++] = (_point) {x, y};
}
}
}
int main() {
int cas = 0;
while(1) {
n = iread(); m = iread();
if(n == 0 && m == 0) break;
for(int i = 1; i <= n; i++) for(int j = 1; j <= m; j++) {
char ch = getchar(); for(; ch < 'A' || ch > 'Z'; ch = getchar());
g[i][j] = ch - 'A' + 1;
vis[i][j] = 0;
}
ans = clo = 0;
for(int i = 1; i <= n; i++) for(int j = 1; j <= m; j++) if(g[i][j] == 1)
clo++, bfs(i, j);
printf("Case %d: %d\n", ++cas, ans);
}
return 0;
}