Compilare: main.cpp: In function 'int main()': main.cpp:45:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < a.size(); ++i) ~~^~~~~~~~~~ main.cpp:46:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 1; j < b.size(); ++j) ~~^~~~~~~~~~ main.cpp:66:49: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] sol[ pd[a.size() - 1][b.size() - 1] ] = NULL; ^~~~