class Solution { public: int numEnclaves(vector<vector<int>>& A) { const int m = A.size(); const int n = A[0].size(); // remove lands connected to 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(begin(A), end(A), 0, [](int s, vector<int>& row) { return s + accumulate(begin(row), end(row), 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); }; };