Add solution #130

Author: JoshCrozier

README.md

@@ -134,6 +134,7 @@
 127|[Word Ladder](./0127-word-ladder.js)|Hard|
 128|[Longest Consecutive Sequence](./0128-longest-consecutive-sequence.js)|Medium|
 129|[Sum Root to Leaf Numbers](./0129-sum-root-to-leaf-numbers.js)|Medium|
+130|[Surrounded Regions](./0130-surrounded-regions.js)|Medium|
 131|[Palindrome Partitioning](./0131-palindrome-partitioning.js)|Medium|
 133|[Clone Graph](./0133-clone-graph.js)|Medium|
 134|[Gas Station](./0134-gas-station.js)|Medium|

solutions/0130-surrounded-regions.js

@@ -0,0 +1,53 @@
+/**
+ * 130. Surrounded Regions
+ * https://leetcode.com/problems/surrounded-regions/
+ * Difficulty: Medium
+ *
+ * You are given an m x n matrix board containing letters 'X' and 'O', capture regions
+ * that are surrounded:
+ * - Connect: A cell is connected to adjacent cells horizontally or vertically.
+ * - Region: To form a region connect every 'O' cell.
+ * - Surround: The region is surrounded with 'X' cells if you can connect the region with
+ * 'X' cells and none of the region cells are on the edge of the board.
+ *
+ * To capture a surrounded region, replace all 'O's with 'X's in-place within the original
+ * board. You do not need to return anything.
+ */
+
+/**
+ * @param {character[][]} board
+ * @return {void} Do not return anything, modify board in-place instead.
+ */
+var solve = function(board) {
+  for (let i = 0; i < board.length; i++) {
+    for (let j = 0; j < board[0].length; j++) {
+      if (board[i][j] === 'O'
+          && (!i || !j || i === board.length - 1 || j === board[0].length - 1)) {
+        dfs(i, j);
+      }
+    }
+  }
+
+  for (let i = 0; i < board.length; i++) {
+    for (let j = 0; j < board[0].length; j++) {
+      if (board[i][j] === '-') {
+        board[i][j] = 'O';
+      } else {
+        board[i][j] = 'X';
+      }
+    }
+  }
+
+  function dfs(i, j) {
+    if (i < 0 || i >= board.length || j < 0 || j >= board[i].length
+        || board[i][j] === '-' || board[i][j] === 'X') {
+      return;
+    }
+
+    board[i][j] = '-';
+    dfs(i - 1, j);
+    dfs(i + 1, j);
+    dfs(i, j - 1);
+    dfs(i, j + 1);
+  }
+};