Add word-search-ii solution in TS

Author: Jeehay28

word-search-ii/Jeehay28.ts

@@ -0,0 +1,86 @@
+// TC: O(K × L + M × N × 4^L)
+// SC: O(K × L + L)
+// K: num of words
+// L: length of the longest word
+
+function findWords(board: string[][], words: string[]): string[] {
+  const result: string[] = [];
+  const root: TrieNode = buildTrie(words);
+  const rows = board.length;
+  const cols = board[0].length;
+
+  function backtrack(row: number, col: number, node: TrieNode) {
+    const char = board[row][col];
+    const nextNode = node[char] as TrieNode;
+
+    if (!nextNode) return;
+
+    const word = nextNode["$"];
+    if (typeof word === "string") {
+      result.push(word);
+      delete nextNode["$"]; // avoid duplicate
+    }
+
+    board[row][col] = ""; // mark as visited
+
+    const directions = [
+      [1, 0],
+      [-1, 0],
+      [0, 1],
+      [0, -1],
+    ];
+
+    for (const [dx, dy] of directions) {
+      const newRow = row + dx;
+      const newCol = col + dy;
+
+      if (
+        newRow >= 0 &&
+        newRow < rows &&
+        newCol >= 0 &&
+        newCol < cols &&
+        board[newRow][newCol] !== "$"
+      ) {
+        backtrack(newRow, newCol, nextNode);
+      }
+    }
+
+    board[row][col] = char;
+  }
+
+  for (let r = 0; r < rows; r++) {
+    for (let c = 0; c < cols; c++) {
+      backtrack(r, c, root);
+    }
+  }
+
+  return result;
+}
+
+// Trie
+// {
+//   "e": {
+//     "a": {
+//       "t": {
+//         "#": "eat"
+//       }
+//     }
+//   }
+// }
+
+type TrieNode = {
+  [key: string]: TrieNode | string;
+};
+
+function buildTrie(words: string[]): TrieNode {
+  const root: TrieNode = {};
+  for (const word of words) {
+    let node = root;
+    for (const char of word) {
+      if (!node[char]) node[char] = {};
+      node = node[char] as TrieNode;
+    }
+    node["$"] = word; // end of word
+  }
+  return root;
+}