題目鏈接：http://poj.org/problem?id=3620 分四個方向dfs，最后找到最大值。
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1 #include <iostream>
2 #include <cstdio>
3 #include <cstdlib>
4 #include <cstring>
5 #include <cmath>
6 #include <algorithm>
7 using namespace std;
8 #define maxl 10000
9 int n, m, k, num, G[110][110], f[110][110];
10 int dir[4][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
11 int dfs(int p, int q)
12 {
13 f[p][q] = 1;
14 for (int i = 0; i < 4; i++)
15 {
16 int x = p + dir[i][0];
17 int y = q + dir[i][1];
18 if (!f[x][y] && G[x][y])
19 {
20 num++;
21 dfs(x, y);
22 }
23 }
24 return num;
25 }
26 int main()
27 {
28 while (~scanf("%d%d%d", &n, &m, &k))
29 {
30 int ans = 0;
31 memset(f, 0, sizeof(f));
32 memset(G, 0, sizeof(G));
33 while (k--)
34 {
35 int x, y;
36 scanf("%d%d", &x, &y);
37 G[x][y] = 1;
38 }
39 for (int i = 1; i <= n; i++)
40 for (int j = 1; j <= m; j++)
41 {
42 if (!f[i][j] && G[i][j])
43 {
44 num = 1;
45 ans = max(ans, dfs(i, j));
46 }
47 }
48 printf("%d\n", ans);
49 }
50 return 0;
51
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