Compilare: main.cpp: In function 'void citire()': main.cpp:21:22: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] mt[i][j]=NULL; ^~~~ main.cpp: In function 'int main()': main.cpp:54:26: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] mt[i][j]=NULL; ^~~~ main.cpp:63:22: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] s[i]=NULL; ^~~~ main.cpp:50:13: warning: unused variable 'ok' [-Wunused-variable] int ok=1; ^~ main.cpp:43:9: warning: unused variable 'nivel' [-Wunused-variable] int nivel=0; ^~~~~