Meta Software Engineer interview questions

Add two big numbers.

Given a 2-d matrix with each cell contains a character from the alphabet. Given a word, verify if the exist in this matrix. A word is called to exist in a matrix if there is a path from cells to cells in the matrix and this path creates a word that matches the word we're looking for. a cell could move to all vertex-adjacent cells (so there are 8 adjacent cells) and cannot use a cell more than once