Create: 0130-surrounded-regions.dart

Author: matthewkeck

dart/0130-surrounded-regions.dart

@@ -0,0 +1,51 @@
+class Solution {
+  late List<List<String>> board;
+  late int rows;
+  late int columns;
+
+  bool isInBound(int row, int column) {
+    return 0 <= row && row < rows && 0 <= column && column < columns;
+  }
+
+  void dfs(int row, int column) {
+    if (!isInBound(row, column) || board[row][column] != 'O') {
+      return;
+    }
+
+    board[row][column] = 'T';
+
+    dfs(row + 1, column);
+    dfs(row, column + 1);
+    dfs(row - 1, column);
+    dfs(row, column - 1);
+  }
+
+  void solve(List<List<String>> board) {
+    this.board = board;
+    rows = board.length;
+    columns = board[0].length;
+
+    // Traverse the first and last columns
+    for (int column = 0; column < columns; column++) {
+      dfs(0, column);
+      dfs(rows - 1, column);
+    }
+
+    // Traverse the first and last rows
+    for (int row = 0; row < rows; row++) {
+      dfs(row, 0);
+      dfs(row, columns - 1);
+    }
+
+    // Replace all 'O' with 'X' and 'T' back to 'O'
+    for (int row = 0; row < rows; row++) {
+      for (int column = 0; column < columns; column++) {
+        if (board[row][column] == 'O') {
+          board[row][column] = 'X';
+        } else if (board[row][column] == 'T') {
+          board[row][column] = 'O';
+        }
+      }
+    }
+  }
+}