Add solution #212

Author: JoshCrozier

0212-word-search-ii.js

@@ -0,0 +1,49 @@
+/**
+ * 212. Word Search II
+ * https://leetcode.com/problems/word-search-ii/
+ * Difficulty: Hard
+ *
+ * Given an m x n board of characters and a list of strings words, return all words on the board.
+ *
+ * Each word must be constructed from letters of sequentially adjacent cells, where adjacent cells
+ * are horizontally or vertically neighboring. The same letter cell may not be used more than once
+ * in a word.
+ */
+
+/**
+ * @param {character[][]} board
+ * @param {string[]} words
+ * @return {string[]}
+ */
+var findWords = function(board, words) {
+  const root = {};
+  const result = new Set();
+  const m = board.length;
+  const n = board[0].length;
+
+  words.forEach(w => w.split('').reduce((n, c) => n[c] = n[c] || {}, root).word = w);
+
+  for (let i = 0; i < m; i++) {
+    for (let j = 0; j < n; j++) {
+      dfs(i, j, root);
+    }
+  }
+
+  return Array.from(result);
+
+  function dfs(i, j, node) {
+    const char = board[i][j];
+    const next = node[char];
+    if (!next) return;
+    if (next.word) {
+      result.add(next.word);
+    }
+    board[i][j] = '#';
+    for (const [di, dj] of [[0, 1], [1, 0], [0, -1], [-1, 0]]) {
+      if (i + di >= 0 && i + di < m && j + dj >= 0 && j + dj < n && board[i + di][j + dj] !== '#') {
+        dfs(i + di, j + dj, next);
+      }
+    }
+    board[i][j] = char;
+  }
+};

README.md

@@ -193,6 +193,7 @@
 209|[Minimum Size Subarray Sum](./0209-minimum-size-subarray-sum.js)|Medium|
 210|[Course Schedule II](./0210-course-schedule-ii.js)|Medium|
 211|[Design Add and Search Words Data Structure](./0211-design-add-and-search-words-data-structure.js)|Medium|
+212|[Word Search II](./0212-word-search-ii.js)|Hard|
 213|[House Robber II](./0213-house-robber-ii.js)|Medium|
 214|[Shortest Palindrome](./0214-shortest-palindrome.js)|Hard|
 215|[Kth Largest Element in an Array](./0215-kth-largest-element-in-an-array.js)|Medium|