Add word-search-ii solution

Author: Jeehay28

word-search-ii/Jeehay28.js

@@ -0,0 +1,104 @@
+// const words = ["oath", "pea", "eat", "rain"];
+// const trie = buildTrie(words);
+
+// Trie in JavaScript Object Notation:
+// {
+//   "o": { "a": { "t": { "h": { "word": "oath" } } } },
+//   "p": { "e": { "a": { "word": "pea" } } },
+//   "e": { "a": { "t": { "word": "eat" } } },
+//   "r": { "a": { "i": { "n": { "word": "rain" } } } }
+// }
+
+class TrieNode {
+  constructor() {
+    this.children = {}; // Stores child nodes (next characters)
+    this.word = null; // Stores the word when a full word is formed
+  }
+}
+
+const buildTrie = (words) => {
+  let root = new TrieNode(); // Create the root node
+
+  for (const word of words) {
+    // Iterate over each word
+    let node = root;
+
+    for (const char of word) {
+      // Iterate over each character in the word
+      if (!node.children[char]) {
+        node.children[char] = new TrieNode(); // Create node if missing
+      }
+      node = node.children[char]; // Move to the next node
+    }
+
+    node.word = word; // Store word at the end node
+  }
+
+  return root;
+};
+
+// ✅ Time Complexity: O(N * L + M * 4^L)
+// ✅ Space Complexity: O(N * L + M)
+
+// N represents the number of words in the words array.
+// L represents the maximum length of a word in the words array.
+// M represents the total number of cells on the board, which is the product of the number of rows and columns: M = rows × cols
+
+/**
+ * @param {character[][]} board
+ * @param {string[]} words
+ * @return {string[]}
+ */
+var findWords = function (board, words) {
+  const root = buildTrie(words);
+  const result = new Set(); // To store found words
+  const rows = board.length,
+    cols = board[0].length;
+
+  const dfs = (node, r, c) => {
+    if (
+      r < 0 ||
+      c < 0 ||
+      r >= rows ||
+      c >= cols ||
+      !node.children[board[r][c]]
+    ) {
+      return;
+    }
+
+    const char = board[r][c];
+    node = node.children[char]; // Move to the next Trie node
+
+    if (node.word) {
+      // If a word is found at this node
+      result.add(node.word); // Add it to the result set
+      node.word = null; // Avoid duplicate results
+    }
+
+    board[r][c] = "#"; // Temporarily mark visited cell
+
+    // Explore all 4 directions
+    dfs(node, r + 1, c);
+    dfs(node, r - 1, c);
+    dfs(node, r, c + 1);
+    dfs(node, r, c - 1);
+
+    board[r][c] = char; // Restore the original character
+
+    // 🔥 Remove node if it has no children (prune Trie)
+    if (Object.keys(node.children).length === 0) {
+      delete node.children[char];
+    }
+  };
+
+  for (let r = 0; r < rows; r++) {
+    for (let c = 0; c < cols; c++) {
+      if (root.children[board[r][c]]) {
+        dfs(root, r, c);
+      }
+    }
+  }
+
+  return Array.from(result);
+};
+