【HDOJ】3329 The Flood

超简单BFS。
  1 /* 3329 */
  2 #include <iostream>
  3 #include <queue>
  4 #include <cstdio>
  5 #include <cstring>
  6 #include <cstdlib>
  7 using namespace std;
  8 
  9 #define MAXN 105
 10 
 11 typedef struct node_t {
 12     int x, y;
 13     node_t() {}
 14     node_t(int xx, int yy) {
 15         x = xx; y = yy;
 16     }
 17 } node_t;
 18 
 19 int n, m, h, total;
 20 int map[MAXN][MAXN];
 21 bool visit[MAXN][MAXN];
 22 int dir[4][2] = {
 23     -1,0,1,0,0,-1,0,1
 24 };
 25 
 26 inline bool check(int x, int y) {
 27     return x<0 || x>=n || y<0 || y>=m;
 28 }
 29 
 30 void border_bfs(int x, int y) {
 31     int i, j, k;
 32     int xx, yy;
 33     queue<node_t> Q;
 34     node_t nd;
 35     
 36     Q.push(node_t(x, y));
 37     visit[x][y] = true;
 38     
 39     while (!Q.empty()) {
 40         nd = Q.front();
 41         Q.pop();
 42         --total;
 43         for (i=0; i<4; ++i) {
 44             xx = nd.x + dir[i][0];
 45             yy = nd.y + dir[i][1];
 46             if (check(xx, yy) || visit[xx][yy] || map[xx][yy]>h)
 47                 continue;
 48             visit[xx][yy] = true;
 49             Q.push(node_t(xx, yy));
 50         }
 51     }
 52 }
 53 
 54 void bfs(int x, int y) {
 55     int xx, yy, s;
 56     int i, j, k;
 57     queue<node_t> Q;
 58     node_t nd;
 59     
 60     Q.push(node_t(x, y));
 61     visit[x][y] = true;
 62     
 63     while (!Q.empty()) {
 64         nd = Q.front();
 65         Q.pop();
 66         --total;
 67         for (i=0; i<4; ++i) {
 68             xx = nd.x + dir[i][0];
 69             yy = nd.y + dir[i][1];
 70             if (check(xx,yy) || visit[xx][yy])
 71                 continue;
 72             visit[xx][yy] = true;
 73             Q.push(node_t(xx, yy));
 74         }
 75     }
 76 }
 77 
 78 int main() {
 79     int t = 0;
 80     int i, j, k, tmp;
 81     bool flag;
 82     int maxh;
 83     
 84     #ifndef ONLINE_JUDGE
 85         freopen("data.in", "r", stdin);
 86         freopen("data.out", "w", stdout);
 87     #endif
 88     
 89     while (scanf("%d %d",&n,&m)!=EOF && (n||m)) {
 90         maxh = -1;
 91         for (i=0; i<n; ++i) {
 92             for (j=0; j<m; ++j) {
 93                 scanf("%d", &map[i][j]);
 94                 if (map[i][j] > maxh)
 95                     maxh = map[i][j];
 96             }
 97         }
 98         tmp = n*m;
 99         for (h=1; h<maxh; ++h) {
100             // handle border of map
101             total = tmp;
102             memset(visit, false, sizeof(visit));
103             for (j=0; j<m; ++j) {
104                 if (!visit[0][j] && map[0][j]<=h)
105                     border_bfs(0, j);
106                 if (!visit[n-1][j] && map[n-1][j]<=h)
107                     border_bfs(n-1, j);
108             }
109             for (i=0; i<n; ++i) {
110                 if (!visit[i][0] && map[i][0]<=h)
111                     border_bfs(i, 0);
112                 if (!visit[i][m-1] && map[i][m-1]<=h)
113                     border_bfs(i, m-1);
114             }
115             // check if there exsits two or more lands
116             flag = false;
117             for (i=0; i<n; ++i) {
118                 for (j=0; j<m; ++j) {
119                     if (!visit[i][j]) {
120                         flag = true;
121                         break;
122                     }
123                 }
124                 if (flag)
125                     break;
126             }
127             if (flag) {
128                 bfs(i, j);
129                 if (total > 0)
130                     break;
131             }
132         }
133         if (h < maxh)
134             printf("Case %d: Island splits when ocean rises %d feet.
", ++t, h);
135         else
136             printf("Case %d: Island never splits.
", ++t);
137     }
138     
139     return 0;
140 }