Compilare: user.cpp: In function ‘int main()’: user.cpp:48:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < ls[x].size(); i++) ^ user.cpp:55:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < ls[x].size(); i++) { ^ user.cpp:69:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < ls[x].size(); i++) { ^ user.cpp:76:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < ls[x].size(); i++) { ^