Compilare: main.cpp: In function 'void solve()': main.cpp:52:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i <= n && mt[i - 1].size() > j && mt[i].size() > j && mt[i][j] == mt[i - 1][j] && mt[i - 1][j] == '1') ~~~~~~~~~~~~~~~~~^~~ main.cpp:52:64: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i <= n && mt[i - 1].size() > j && mt[i].size() > j && mt[i][j] == mt[i - 1][j] && mt[i - 1][j] == '1') ~~~~~~~~~~~~~^~~ main.cpp: In function 'void c2()': main.cpp:78:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < mt[i].size(); ++j) ~~^~~~~~~~~~~~~~