Create number-of-enclaves.cpp

Author: kamyu104

C++/number-of-enclaves.cpp

@@ -0,0 +1,35 @@
+// Time:  O(m * n)
+// Space: O(m * n)
+
+class Solution {
+public:
+    int numEnclaves(vector<vector<int>>& A) {
+        for (int i = 0; i < A.size(); ++i) {
+            dfs(&A, i, 0);
+            dfs(&A, i, A[0].size() - 1);
+        }
+        for (int j = 1; j < A[0].size() - 1; ++j) {
+            dfs(&A, 0, j);
+            dfs(&A, A.size() - 1, j);
+        }
+        return accumulate(A.cbegin(), A.cend(), 0,
+                          [](int sum, const vector<int>& row) {
+                              return sum + accumulate(row.cbegin(), row.cend(), 0);
+                          });
+    }
+
+private:
+    void dfs(vector<vector<int>> *A, int i, int j) {
+        static const vector<pair<int, int>> directions{{0, 1}, {1, 0},
+                                                       {0, -1}, {-1, 0}};
+        if (!(0 <= i && i < A->size() &&
+              0 <= j && j < (*A)[0].size() &&
+              (*A)[i][j])) {
+            return;
+        }
+        (*A)[i][j] = 0;
+        for (const auto& d : directions) {
+            dfs(A, i + d.first, j + d.second);
+        }
+    }
+};