Compilare: main.cpp: In function 'void Clean()': main.cpp:27:41: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] for(int i=strlen(c)-1;i>=0;i--)c[i]=NULL; ^~~~ main.cpp: In function 'void B(bool)': main.cpp:36:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(j+4>=strlen(c))ok=0; ~~~^~~~~~~~~~~ main.cpp: In function 'void C()': main.cpp:47:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(c[j]=='2'&&j==strlen(c)-1)ok=1; ~^~~~~~~~~~~~~ main.cpp:48:49: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(c[j]=='1'&&c[j+1]=='2'&&(strlen(c)-1==j+2))ok=1; ~~~~~~~~~~~^~~~~