Feat: 212. Word Search II

Author: HC-kang

word-search-ii/HC-kang.ts

@@ -0,0 +1,62 @@
+/**
+ * https://leetcode.com/problems/word-search-ii
+ * T.C. O(W * L + M * N * 4^L) W: number of words, L: mean length of words, M: rows, N: cols
+ * S.C. O(W * L)
+ */
+function findWords(board: string[][], words: string[]): string[] {
+  const root = new TrieNode();
+  for (const word of words) {
+    let node = root;
+    for (const char of word) {
+      if (!node.children[char]) {
+        node.children[char] = new TrieNode();
+      }
+      node = node.children[char];
+    }
+    node.word = word;
+    node.isEnd = true;
+  }
+
+  const result = new Set<string>();
+  const rows = board.length;
+  const cols = board[0].length;
+
+  function dfs(row: number, col: number, node: TrieNode): void {
+    if (row < 0 || row >= rows) return;
+    if (col < 0 || col >= cols) return;
+    if (!board[row][col]) return;
+    if (!node.children[board[row][col]]) return;
+
+    const char = board[row][col];
+    const currNode = node.children[char];
+
+    if (currNode.isEnd) {
+      result.add(currNode.word);
+    }
+
+    board[row][col] = '#';
+
+    dfs(row + 1, col, currNode);
+    dfs(row - 1, col, currNode);
+    dfs(row, col + 1, currNode);
+    dfs(row, col - 1, currNode);
+
+    board[row][col] = char;
+  }
+
+  for (let i = 0; i < rows; i++) {
+    for (let j = 0; j < cols; j++) {
+      dfs(i, j, root);
+    }
+  }
+
+  return Array.from(result);
+}
+
+class TrieNode {
+  constructor(
+    public children: Record<string, TrieNode> = {},
+    public word: string = '',
+    public isEnd: boolean = false
+  ) {}
+}