Fixed

I mentioned in the first sentence that the travelers are going to the trip along the river, but I will try to clarify the description. English is not my primary language too, so please let me know, if I make any silly mistakes.

Full test suie compiles with warnings:

In file included from main.cpp:7:
./tests.cpp:21:27: warning: comparison of integers of different signs: 'int' and 'unsigned long' [-Wsign-compare]
        for (int i = 0; i < tempPath.length() - 1; i++)
                        ~ ^ ~~~~~~~~~~~~~~~~~~~~~
1 warning generated.

I would also suggest adding message suppliers to assertions, at least in some basic/small random tests, for better feedback on failure. For details see https://docs.codewars.com/languages/cpp/authoring#custom-assertion-messages .

English is not my primary language so it might be a language issue, but for me initially it was not really clear what "crossing the river" means and why I need to account for all tributaries. Cannot travellers just, like, cross the river and move from the left bank to the right bank, so cost would be always 1? It took me a while to understand that the travellers want to trip along the whole river, starting at source, and reaching its estuary (word?).

Fixed

Fixed

Fixed. Thanks:)

#include <iostream> shouldn't be added to the initial code.

Needs random test cases, but otherwise looks good. Fun kata!