Compilare: main.cpp: In function 'void add_string()': main.cpp:73:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp:140:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(sol.size()<k) ~~~~~~~~~~^~ main.cpp: In function 'int tolit(char)': main.cpp:16:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ main.cpp: In function 'char tochar(int)': main.cpp:25:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ main.cpp: In function 'int who_beats(int)': main.cpp:69:1: warning: control reaches end of non-void function [-Wreturn-type] } ^