Merge pull request neetcode-gh#699 from arthurgarzajr/main

Adding 130-Surrounded-Regions.swift

swift/130-Surrounded-Regions.swift

@@ -0,0 +1,48 @@
+class Solution {
+ func solve(_ board: inout [[Character]]) {
+ var rows = board.count
+ var columns = board[0].count
+
+ // 1. DFS Capture unsurrounded regions (O -> T)
+ for r in 0..<rows {
+ for c in 0..<columns {
+ if board[r][c] == "O" &&
+ ([0, rows - 1].contains(r) || [0, columns - 1].contains(c)) {
+ capture(r, c, &board)
+ }
+ }
+ }
+
+ // 2. Capture surrounded regions (O -> X)
+ for r in 0..<rows {
+ for c in 0..<columns {
+ if board[r][c] == "O" {
+ board[r][c] = Character("X")
+ }
+ }
+ }
+
+ // 3. Uncapture surrounded regions (T -> O)
+ for r in 0..<rows {
+ for c in 0..<columns {
+ if board[r][c] == "T" {
+ board[r][c] = Character("O")
+ }
+ }
+ }
+ }
+
+ func capture(_ r: Int, _ c: Int, _ board: inout [[Character]]) {
+ // Make sure r and c are in bounds
+ guard r >= 0, r < board.count, c >= 0, c < board[0].count, board[r][c] == "O" else {
+ return
+ }
+
+ board[r][c] = Character("T")
+
+ capture(r - 1, c, &board)
+ capture(r + 1, c, &board)
+ capture(r, c - 1, &board)
+ capture(r, c + 1, &board)
+ }
+}