class Solution {
public:
int numEnclaves(vector<vector<int>>& A) {
const int m = A.size();
const int n = A[0].size();
// Remove the lands connected to the edge.
for (int i = 0; i < m; ++i)
for (int j = 0; j < n; ++j)
if (i * j == 0 || i == m - 1 || j == n - 1)
if (A[i][j] == 1)
dfs(A, i, j);
return accumulate(A.begin(), A.end(), 0, [](int s, vector<int>& row) {
return s + accumulate(row.begin(), row.end(), 0);
});
}
private:
void dfs(vector<vector<int>>& A, int i, int j) {
if (i < 0 || i == A.size() || j < 0 || j == A[0].size())
return;
if (A[i][j] == 0)
return;
A[i][j] = 0;
dfs(A, i + 1, j);
dfs(A, i - 1, j);
dfs(A, i, j + 1);
dfs(A, i, j - 1);
};
};