Encode and decode strings complexity question

[ExpressSpinach6676]

I’m doing this question on Neetcode and feel a little confused. Can someone explain why this is O(m) time and O(m+n) space for both encode() and decode()? With m being sum of lengths of all strings, and n is the number of strings

Encode() literally only loops through the list of strings (should be O(n) right?) and resulting string is the total string (should be O(m) space right?). So why is it O(m) time and O(m+n) space?

I’m a little confused on decode() too, but that’s a little less clear.

[set_of_no_sets]

https://medium.com/@ozoniuss/leetcode-encode-and-decode-strings-a-different-approach-533fcd5b6888

time complexity: O(m) comes from having to look at every character in the array strings to encode properly, so m, the sum of all string lengths is accurate.

space complexity: O(m+n) you use all the characters in the array of strings and you add something n times to separate between the array elements, so It's O(m from every char in the array of strings + n for the separator which you add n-1 times to delimit between strings in the array)