Compilare: main.cpp: In function 'int main()': main.cpp:50:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( i = 0; i < lvl.size(); i ++ ) ~~^~~~~~~~~~~~ main.cpp:52:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( j = 1; (1 << j) <= lvl.size(); j ++ ) ~~~~~~~~~^~~~~~~~~~~~~ main.cpp:53:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( i = 0; i + (1<<j) - 1 < lvl.size(); i ++ ) { ~~~~~~~~~~~~~~~^~~~~~~~~~~~