Compilare: main.cpp: In function 'int main()': main.cpp:42:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (size_t i = 0; i < x && k < y; i++) ~~^~~ main.cpp:62:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (size_t i = 0; i < x && k < y; i++) ~~^~~ main.cpp: In function 'void prim()': main.cpp:20:10: warning: iteration 1000001 invokes undefined behavior [-Waggressive-loop-optimizations] if (v[i] == false) ~~~^ main.cpp:18:23: note: within this loop for (size_t i = 2; i <= nmax; i++) ^