Word Search

Problem Statement

Given an m x n grid of characters board and a string word, return true if word exists in the grid.

The word can be constructed from letters of sequentially adjacent cells, where adjacent cells are horizontally or vertically neighboring. The same letter cell may not be used more than once.

LeetCode link

Example 1:

Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "ABCCED"
Output: true

Example 2:

Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "SEE"
Output: true

Example 3:

Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "ABCB"
Output: false

Code

Java Code

public class Solution {

    public boolean exist(char[][] board, String word) {
        if (board == null || board.length == 0 || board[0].length == 0 || word == null || word.equals("")) {
            return false;
        }
        for (int i = 0; i < board.length; i ++) {
            for (int j = 0; j < board[0].length; j ++) {
                if (search(board, word, i, j, 0) == true) {
                    return true;
                }
            }
        }
        return false;
    }
    private boolean search(char[][] board, String word, int i, int j, int matched) {
        if (matched == word.length()) {
            return true;
        }
        if (i < 0 || j < 0 || i >= board.length || j >= board[0].length || board[i][j] != word.charAt(matched)) {
            return false;
        }
        board[i][j] = '#';
        boolean result = search(board, word, i - 1, j, matched + 1) || search(board, word, i, j - 1, matched + 1) || search(board, word, i + 1, j, matched + 1) ||  search(board, word, i, j + 1, matched + 1);
        board[i][j] = word.charAt(matched);
        return result;

    }

}