What is the Time Complexity of Go's `append` Function and String Concatenation?

Big O Analysis of Append in Go

Go's built-in append function allows programmers to add elements to the end of a slice. Its time complexity and memory usage are crucial considerations for maintaining efficient code.

Regarding time complexity, append performs the following operations:

• If the destination slice has sufficient capacity, it reslices it, which is a constant time operation.
• If the destination slice's capacity is insufficient, it must allocate new memory, copy the existing elements, append the new elements, and then update the slice header, which is O(n), where n is the length of the slice.

Therefore, the time complexity of append for slices is O(1) if there is sufficient capacity and O(n) otherwise.

Considering string concatenation with the operator, Go creates a new string object each time, resulting in O(n^2) time complexity for concatenating n strings. It copies the entire contents of the existing strings into the new string, leading to significant memory usage and inefficiency.

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