八连块
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题目:输入一个n*n的黑白图像(1表示黑色,0表示白色),任务是统计其中八连块的个数。如果两个黑格子有公共边或者公共顶点,就说它们属于同一个八连块。如图表示3个八连块
-
- #include <stdio.h>
- #include <string.h>
- #define MAX 100
-
- int mat[MAX][MAX], vis[MAX][MAX];
-
- void dfs(int x, int y)
- {
- if (!mat[x][y] || vis[x][y])
- {
- return;
- }
- vis[x][y] = 1;
-
-
- dfs(x-1, y-1); dfs(x-1, y); dfs(x-1, y+1);
- dfs(x, y-1); dfs(x, y+1);
- dfs(x+1, y-1); dfs(x+1, y); dfs(x+1, y+1);
- }
-
- int main(void)
- {
- int n, i, j;
- int count;
- char s[MAX];
- memset(mat, 0, sizeof(mat));
- memset(vis, 0, sizeof(vis));
- scanf("%d", &n);
- for (i=0; i< n; i++)
- {
- memset(s, 0, sizeof(s));
- scanf("%s", s);
- for (j=0; j<n; j++)
- {
- mat[i+1][j+1] = s[j] - '0';
- }
- }
- count = 0;
- for (i=1; i<=n; i++)
- {
- for (j=1; j<=n; j++)
- {
- if (!vis[i][j] && mat[i][j])
- {
- count++;
- dfs(i, j);
- }
- }
- }
- printf("%d\n", count);
- return 0;
- }
DFS(Depth-First Search) 用到的是栈,递归调用时会把局部变量(当前结点编号)存入栈帧中,如果图像太大,递归方式的DFS有栈溢出的危险。为保险起见,可以用显式栈来代替递归调用。如下
-
- #include <stdio.h>
- #include <string.h>
- #define MAX 100
-
- int mat[MAX][MAX], vis[MAX][MAX];
- int s[MAX];
-
- int dx[8] = {-1,-1,-1,0,0,1,1,1};
- int dy[8] = {-1,0,1,-1,1,-1,0,1};
-
- void dfs(int x, int y)
- {
- int u = x*8+y;
- int top = 0;
- s[top++] = u;
- vis[x][y] = 1;
- while (top)
- {
- u = s[--top];
- x = u/8; y = u%8;
- for (int d=0; d<8; d++)
- {
- int nx = x + dx[d], ny = y + dy[d];
- if (mat[nx][ny] && !vis[nx][ny])
- {
- int v = nx * 8 + ny;
- vis[nx][ny] = 1;
- s[top++] = v;
- d = -1;
- x = nx; y = ny;
- }
- }
- }
- }
-
- int main(void)
- {
- int n, i, j;
- int count;
- char s[MAX];
- memset(mat, 0, sizeof(mat));
- memset(vis, 0, sizeof(vis));
- scanf("%d", &n);
- for (i=0; i< n; i++)
- {
- memset(s, 0, sizeof(s));
- scanf("%s", s);
- for (j=0; j<n; j++)
- {
- mat[i+1][j+1] = s[j] - '0';
- }
- }
- count = 0;
- for (i=1; i<=n; i++)
- {
- for (j=1; j<=n; j++)
- {
- if (!vis[i][j] && mat[i][j])
- {
- count++;
- dfs(i, j);
- }
- }
- }
- printf("%d\n", count);
- return 0;
- }
0 0