This is incorrect, under deliriums pedantic interpretation of space complexity. Some regular expressions require one to accept a certain number of examples of a character. This means that storage space for the count is required, which scales logarithmically in the count.

How many times would you need to execute line 2? The more times you need to do this, the more values x needs to be able to represent. So running x++ in O(n) time means the space needed to store the accumulation grows as O(n log_2 n)... under delirium's "pedantic" interpretation of space complexity.

Unknowingly you have allowed me to stumble onto an actual algorithm with O(1) storage pace, that is, one where there are n numbers, and you want to calculated the modulo-k sum. In this case, the algorithm scales logarithmically in the constant parameter k, but O(1) in n.