Compilare: user.cpp: In function ‘int main()’: user.cpp:21:57: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] if((s[j-1]!=' ')&&(s[j]==' ')){if(b>0){s1[a][b]=NULL;a++;b=0;}} ^ user.cpp:11:43: warning: unused variable ‘k1’ [-Wunused-variable] int i,t=0,n,y=0,j,nr,u,a=0,m,r1=0,b=0,k1,r2=0; ^ user.cpp:11:46: warning: variable ‘r2’ set but not used [-Wunused-but-set-variable] int i,t=0,n,y=0,j,nr,u,a=0,m,r1=0,b=0,k1,r2=0; ^