Why is this so much slower in C++?

Question

I have converted this simple method from C# to C++. It reads a path table and populates a list of lists of ints (or a vector of vectors of ints).

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Answer 1

Haven't tested the code but how many ints does it typically load? Consider what happens when each of your vectors reaches its capacity. A vector grows inefficiently - O(n) I believe. C#'s List doesn't have this behaviour.

Consider using std::deque, std::list or some other container that has better growth behaviour. See this article for more info.