Careercup - Facebook面试题 - 5998719358992384

2014-05-02 00:22

题目链接

原题：

Given a matrix consisting of 0's and 1's, find the largest connected component consisting of 1's.

题目：给定一个01矩阵，找出由1构成的连通分量中最大的一个。

解法：四邻接还是八邻接也不说，我就当四邻接了。这种Flood Fill问题，可以用BFS或者DFS解决。

代码：

 1 // http://www.careercup.com/question?id=5998719358992384

 2 #include <vector>

 3 using namespace std;

 4 

 5 class Solution {

 6 public:

 7     int maxConnectedComponent(vector<vector<int> > &v) {

 8         n = (int)v.size();

 9         if (n == 0) {

10             return 0;

11         }

12         m = (int)v[0].size();

13         if (m == 0) {

14             return 0;

15         }

16         

17         int res, max_res;

18         

19         max_res = 0;

20         for (i = 0; i < n; ++i) {

21             for (j = 0; j < m; ++j) {

22                 if (!v[i][j]) {

23                     continue;

24                 }

25                 res = 0;

26                 

27                 v[i][j] = 0;

28                 ++res;

29                 DFS(v, i, j, res);

30                 max_res = res > max_res ? res : max_res;

31             }

32         }

33         

34         return max_res;

35     };

36 private:

37     int n, m;

38     

39     void DFS(vector<vector<int> > &v, int i, int j, int &res) {

40         static const int d[4][2] = {

41             {-1,  0}, 

42             { 0, -1}, 

43             {+1,  0}, 

44             { 0, +1}

45         };

46         

47         int k, x, y;

48         for (k = 0; k < 4; ++k) {

49             x = i + d[k][0];

50             y = j + d[k][1];

51             if (x < 0 || x > n - 1 || y < 0 || y > m - 1) {

52                 continue;

53             }

54             if (!v[x][y]) {

55                 continue;

56             }

57             v[x][y] = 0;

58             ++res;

59             DFS(v, x, y, res);

60         }

61     };

62 };