Create 130-Surrounded-Regions.cs

Author: agnihotriketan

Diff for: csharp/130-Surrounded-Regions.cs

@@ -0,0 +1,50 @@
+public class Solution {
+    public void Solve(char[][] board) {
+        var n = board.Length;
+
+        if (n == 0) return;
+        var m = board[0].Length;
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                if ((i == 0 || j == 0 || i == n - 1 || j == m - 1) && board[i][j] == 'O') {
+                    CaptureDfs(board, i, j);
+                }
+            }
+        }
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                if (board[i][j] == 'O') {
+                    board[i][j] = 'X';
+                }
+            }
+        }
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                if (board[i][j] == 'T') {
+                    board[i][j] = 'O';
+                }
+            }
+        }
+    }
+
+    private void CaptureDfs(char[][] board, int x, int y) {
+        var n = board.Length;
+        var m = board[0].Length;
+
+        if (x >= n || x < 0 || y >= m || y < 0) {
+            return;
+        }
+
+        if (board[x][y] == 'T' || board[x][y] == 'X') return;
+
+        board[x][y] = 'T';
+        CaptureDfs(board, x+1, y); 
+        CaptureDfs(board, x-1, y); 
+        CaptureDfs(board, x, y+1); 
+        CaptureDfs(board, x, y-1); 
+
+    }
+}