Word Search

Author: TonyKim9401

word-search/TonyKim9401.java

@@ -0,0 +1,52 @@
+// TC: O(n * m * 4^k);
+// -> The size of board: n * m
+// -> Check 4 directions by the given word's length: 4^k
+// SC: O(n * m + k)
+// -> boolean 2D array: n * M
+// -> recursive max k spaces
+class Solution {
+    public boolean exist(char[][] board, String word) {
+        // Mark visited path to do not go back.
+        boolean[][] visit;
+
+        for (int i = 0; i < board.length; i++) {
+            for (int j = 0; j < board[0].length; j++) {
+                visit = new boolean[board.length][board[0].length];
+                if (wordSearch(i, j, 0, word, board, visit)) return true;
+            }
+        }
+        return false;
+    }
+
+    private boolean wordSearch(int i, int j, int idx, String word, char[][] board, boolean[][] visit) {
+
+        // When idx checking reach to the end of the length of the word then, return true
+        if (idx == word.length()) return true;
+
+        // Check if i and j are inside of the range
+        if (i < 0 || i >= board.length || j < 0 || j >= board[0].length) return false;
+
+        // Check if the coordinate equals to the charactor value
+        if (board[i][j] != word.charAt(idx)) return false;
+        if (visit[i][j]) return false;
+
+        // Mark the coordinate as visited
+        visit[i][j] = true;
+
+        // If visited, the target is gonna be the next charactor
+        idx += 1;
+
+        // If any direction returns true then it is true
+        if (
+            wordSearch(i+1, j, idx, word, board, visit) ||
+            wordSearch(i-1, j, idx, word, board, visit) ||
+            wordSearch(i, j+1, idx, word, board, visit) ||
+            wordSearch(i, j-1, idx, word, board, visit)
+        ) return true;
+
+        // If visited wrong direction, turns it as false
+        visit[i][j] = false;
+
+        return false;
+    }
+}