add Word Search II solution

Author: HoonDongKang

word-search-ii/HoonDongKang.ts

@@ -0,0 +1,74 @@
+/**
+ * [Problem]: [212] Word Search II
+ * (https://leetcode.com/problems/word-search-ii/)
+ */
+
+class TrieNode {
+    children: Map<string, TrieNode> = new Map();
+    word: string | null = null;
+}
+
+//시간복잡도 O(m * n * 4^s)
+//공간복잡도 O(trie 저장 공간(word * length) + result)
+function findWords(board: string[][], words: string[]): string[] {
+    const result: string[] = [];
+    const rows = board.length;
+    const cols = board[0].length;
+
+    const root = new TrieNode();
+    for (const word of words) {
+        let node = root;
+
+        for (const char of word) {
+            if (!node.children.has(char)) {
+                node.children.set(char, new TrieNode());
+            }
+            node = node.children.get(char)!;
+        }
+
+        node.word = word;
+    }
+
+    const dfs = (i: number, j: number, node: TrieNode) => {
+        const char = board[i][j];
+        const next = node.children.get(char);
+        if (!next) return;
+
+        if (next.word) {
+            result.push(next.word);
+            next.word = null;
+        }
+
+        board[i][j] = "#";
+
+        const directions = [
+            [0, 1],
+            [1, 0],
+            [0, -1],
+            [-1, 0],
+        ];
+
+        for (const [dx, dy] of directions) {
+            const ni = i + dx;
+            const nj = j + dy;
+
+            if (ni >= 0 && ni < rows && nj >= 0 && nj < cols && board[ni][nj] !== "#") {
+                dfs(ni, nj, next);
+            }
+        }
+
+        board[i][j] = char;
+
+        if (next.children.size === 0) {
+            node.children.delete(char);
+        }
+    };
+
+    for (let i = 0; i < rows; i++) {
+        for (let j = 0; j < cols; j++) {
+            dfs(i, j, root);
+        }
+    }
+
+    return result;
+}