For this question, we give you 3 strings and we ask if it is possible to make the 3rd string by merging the 2 other strings. What we mean by merging is that we can cut up both strings into a series of substrings that can be combined to form a 3rd string. The relative order in which characters appear in the first 2 strings must be maintained. Furthermore, you cannot take parts of the first 2 strings to make the 3rd string, all characters must be used when merging.

s1: First string

s2: Second string

s3: Target string that the other 2 strings must be combined to make

Whether or not the 3rd string can be made

s1 = abe

s2 = cdf

s3 = abcdef

Output: true

We can make abcdef by doing ab + cd + e + f = abcdef

s1 = abe

s2 = cdf

s3 = abcd

Output: false

We cannot use parts of the first 2 strings as stated in the problem description so therefore this is not possible.

1 <= s1.length, s2.length, s3.length <= 500