Compilare: user.cpp: In function ‘int main()’: user.cpp:122:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < ans.size(); i++){ ^ user.cpp: In function ‘int toOp(char)’: user.cpp:50:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘int main()’: user.cpp:102:15: warning: ‘c’ may be used uninitialized in this function [-Wmaybe-uninitialized] int a, b, c; ^