Word Search

				
					class Solution {
    public boolean exist(char[][] board, String word) {
        for (int i = 0; i < board.length; i++) {
            for (int j = 0; j < board[i].length; j++) {
                if (backtrack(board, word, i, j, 0)) return true;
            }
        }
        return false;
    }

    private boolean backtrack(char[][] board, String word, int i, int j, int index) {
        if (index == word.length()) return true;
        if (i < 0 || i >= board.length || j < 0 || j >= board[i].length || board[i][j] != word.charAt(index)) return false;

        char temp = board[i][j];
        board[i][j] = '*';
        boolean found = backtrack(board, word, i + 1, j, index + 1) ||
                        backtrack(board, word, i - 1, j, index + 1) ||
                        backtrack(board, word, i, j + 1, index + 1) ||
                        backtrack(board, word, i, j - 1, index + 1);
        board[i][j] = temp;
        return found;
    }
}