Compilare: user.cpp: In function ‘int main()’: user.cpp:80:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < lst[k].size(); ++i) { ^ user.cpp:89:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < lst[k].size(); ++i) { ^ user.cpp:102:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < lst[0].size(); ++i) ^ user.cpp:103:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < lst[0][i].size(); ++j) ^ user.cpp:109:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < lst[0].size(); ++i) { ^