Compilare: user.cpp: In function ‘int main()’: user.cpp:74:57: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(v[i].c>=4 && strlen(nr2)+2<=n/2+n%2) ^ user.cpp:93:32: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] else ch=NULL; ^ user.cpp:100:32: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] else ch=NULL; ^ user.cpp:129:28: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] else ch=NULL; ^ user.cpp:136:28: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] else ch=NULL; ^ user.cpp:141:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(!(strlen(nr2)+2<=n/2)) ^ user.cpp:158:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(v[1].c>=4 && strlen(nr2)+2<=l) ^ user.cpp:175:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(strlen(nr2)+2<=l<0) ^ user.cpp:175:33: warning: comparisons like ‘X<=Y<=Z’ do not have their mathematical meaning [-Wparentheses] if(strlen(nr2)+2<=l<0) ^ user.cpp:197:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(v[i].c>4 && strlen(nr2)+2<=l) ^ user.cpp:199:50: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(v[i].c>4 && strlen(nr2)+2<=l) ^ user.cpp:208:48: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(v[i].c>=2 && strlen(nr2)+2<=l) ^ user.cpp:217:32: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] else ch=NULL; ^ user.cpp:224:32: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] else ch=NULL; ^ user.cpp:229:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(!(strlen(nr2)+2<=l)) ^ user.cpp:252:28: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] else ch=NULL; ^ user.cpp:259:28: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null]