【HDOJ】2782 The Worm Turns

DFS。
  1 /* 2782 */
  2 #include <iostream>
  3 #include <queue>
  4 #include <cstdio>
  5 #include <cstring>
  6 #include <cstdlib>
  7 using namespace std;
  8 
  9 #define MAXN 650
 10 
 11 int n, m;
 12 bool visit[MAXN][MAXN];
 13 int ansd, ansx, ansy, ansb;
 14 int dir[4][2] = {
 15      // E, N, S, W.
 16      0,1, -1,0, 1,0, 0,-1
 17 };
 18 int link[4][2] = {
 19     1,2, 0,3, 0,3, 1,2
 20 };
 21 char op[5] = "ENSW";
 22 
 23 
 24 inline bool check(int x, int y) {
 25     return x<0 || x>=n || y<0 || y>=m; 
 26 }
 27 
 28 int dfs(int x, int y, int d) {
 29     int i, j, k, tmp;
 30     int xx, yy;
 31     int ret = 0;
 32     
 33     if (d == -1) {
 34         for (i=0; i<4; ++i) {
 35             xx = x + dir[i][0];
 36             yy = y + dir[i][1];
 37             if (check(xx, yy) || visit[xx][yy])
 38                 continue;
 39             k = 0;
 40             while (!check(xx, yy) && !visit[xx][yy]) {
 41                 ++k;
 42                 visit[xx][yy] = true;
 43                 xx += dir[i][0];
 44                 yy += dir[i][1];
 45             }
 46             xx -= dir[i][0];
 47             yy -= dir[i][1];
 48             tmp = k + dfs(xx, yy, i);
 49             if (tmp > ansb) {
 50                 ansb = tmp;
 51                 ansx = x;
 52                 ansy = y;
 53                 ansd = i;
 54             }
 55             while (k--) {
 56                 visit[xx][yy] = false;
 57                 xx -= dir[i][0];
 58                 yy -= dir[i][1];
 59             }
 60         }
 61     } else {
 62         for (j=0; j<2; ++j) {
 63             i = link[d][j];
 64             xx = x + dir[i][0];
 65             yy = y + dir[i][1];
 66             if (check(xx, yy) || visit[xx][yy])
 67                 continue;
 68             k = 0;
 69             while (!check(xx, yy) && !visit[xx][yy]) {
 70                 ++k;
 71                 visit[xx][yy] = true;
 72                 xx += dir[i][0];
 73                 yy += dir[i][1];
 74             }
 75             xx -= dir[i][0];
 76             yy -= dir[i][1];
 77             tmp = k + dfs(xx, yy, i);
 78             if (tmp > ret)
 79                 ret = tmp;
 80             while (k--) {
 81                 visit[xx][yy] = false;
 82                 xx -= dir[i][0];
 83                 yy -= dir[i][1];
 84             }
 85         }
 86     }
 87     return ret;
 88 }
 89 
 90 int main() {
 91     int t = 0;
 92     int i, j, k;
 93     
 94     #ifndef ONLINE_JUDGE
 95         freopen("data.in", "r", stdin);
 96     #endif
 97     
 98     while (scanf("%d %d",&n,&m)!=EOF && (n||m)) {
 99         memset(visit, false, sizeof(visit));
100         scanf("%d", &k);
101         while (k--) {
102             scanf("%d %d", &i, &j);
103             visit[i][j] = true;
104         }
105         ansb = -1;
106         for (i=0; i<n; ++i) {
107             for (j=0; j<m; ++j) {
108                 if (!visit[i][j]) {
109                     visit[i][j] = true;
110                     dfs(i, j, -1);
111                     visit[i][j] = false;
112                 }
113             }
114         }
115         printf("Case %d: %d %d %d %c
", ++t, ansb+1, ansx, ansy, op[ansd]);
116     }
117     
118     return 0;
119 }