Compilare: main.cpp: In function 'int factor()': main.cpp:14:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (curr < s.size() and isdigit(s[curr])) ans = ans * 10 + (int)(s[curr++] - '0'); ~~~~~^~~~~~~~~~ main.cpp: In function 'int termen()': main.cpp:20:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (curr < s.size()) { ~~~~~^~~~~~~~~~ main.cpp: In function 'int solve()': main.cpp:30:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (curr < s.size()) { ~~~~~^~~~~~~~~~