#79 - Word Search

Medium • View on LeetCode • View on GitHub

Problem Description

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.

Solution

/**
 * @param {character[][]} board
 * @param {string} word
 * @return {boolean}
 */
var exist = function(board, word) {
  function backtrack(x, y, k) {
    if (board[x][y] !== word[k]) {
      return false;
    } else if (k === word.length - 1) {
      return true;
    }

    board[x][y] = '-';

    for (const direction of [[-1, 0], [0, 1], [1, 0], [0, -1]]) {
      const [i, j] = [x + direction[0], y + direction[1]];
      if (i >= 0 && i < board.length && j >= 0 && j < board[0].length) {
        if (backtrack(i, j, k + 1)) {
          return true;
        }
      }
    }

    board[x][y] = word[k];

    return false;
  }

  for (let i = 0; i < board.length; i++) {
    for (let j = 0; j < board[0].length; j++) {
      if (backtrack(i, j, 0)) {
        return true;
      }
    }
  }

  return false;
};