Add week 4 solutions: word-search

Author: gitsunmin

word-search/gitsunmin.ts

@@ -0,0 +1,33 @@
+/**
+ * https://leetcode.com/problems/word-search
+ * time complexity : O(m * n * 4^L)
+ * space complexity : O(L)
+ */
+const dfs = (r: number, c: number, index: number, board: string[][], word: string, rows: number, cols: number): boolean => {
+    if (index === word.length) return true;
+
+    if (r < 0 || r >= rows || c < 0 || c >= cols || board[r][c] !== word[index]) return false;
+    const temp = board[r][c];
+
+    board[r][c] = '🚪';
+    const found = dfs(r + 1, c, index + 1, board, word, rows, cols) ||
+        dfs(r - 1, c, index + 1, board, word, rows, cols) ||
+        dfs(r, c + 1, index + 1, board, word, rows, cols) ||
+        dfs(r, c - 1, index + 1, board, word, rows, cols);
+
+    board[r][c] = temp;
+
+    return found;
+};
+
+function exist(board: string[][], word: string): boolean {
+    const rows = board.length;
+    const cols = board[0].length;
+
+    for (let r = 0; r < rows; r++) {
+        for (let c = 0; c < cols; c++) {
+            if (dfs(r, c, 0, board, word, rows, cols)) return true;
+        }
+    }
+    return false;
+}