merge to store the result.i and j to traverse word1 and word2 respectively.word1 and word2 are non-empty:
a. If the current character of word1 is greater than word2, append it to merge and increment i.
b. If the current character of word2 is greater than word1, append it to merge and increment j.
c. If the current characters are equal, compare the substrings from the current indices to the end.
d. Append the character from the string with the lexicographically larger substring and increment the respective pointer.merge.merge string.