先将所有和边界相邻的1标记成0,所有没有标记过的陆地就是答案。也就是对边界做flood fill算法
class Solution {
public:
int n, m;
vector<vector<int>> g;
int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
void dfs(int x, int y) {
g[x][y] = 0;
for (int i = 0; i < 4; i ++ ) {
int a = x + dx[i], b = y + dy[i];
if (a >= 0 && a < n && b >= 0 && b < m && g[a][b])
dfs(a, b);
}
}
int numEnclaves(vector<vector<int>>& grid) {
g = grid;
n = g.size();
m = g[0].size();
for (int i = 0; i < n; i ++ )
for (int j = 0; j < m; j ++ )
if (!i || !j || i == n - 1 || j == m - 1)
if (g[i][j])
dfs(i, j);
int res = 0;
for (int i = 0; i < n; i ++ )
for (int j = 0; j < m; j ++ )
res += g[i][j];
return res;
}
};