Compilare: main.cpp: In function 'void citire()': main.cpp:22:22: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] mt[i][j]=NULL; ^~~~ main.cpp: In function 'int main()': main.cpp:55:26: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] mt[i][j]=NULL; ^~~~ main.cpp:64:22: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] s[i]=NULL; ^~~~ main.cpp:51:13: warning: unused variable 'ok' [-Wunused-variable] int ok=1; ^~ main.cpp:44:9: warning: unused variable 'nivel' [-Wunused-variable] int nivel=0; ^~~~~ main.cpp: In function 'void citire()': main.cpp:22:21: warning: iteration 50 invokes undefined behavior [-Waggressive-loop-optimizations] mt[i][j]=NULL; ^ main.cpp:21:23: note: within this loop for(int j=0; j<=50; ++j) ~^~~~ main.cpp: In function 'int main()': main.cpp:55:25: warning: iteration 50 invokes undefined behavior [-Waggressive-loop-optimizations] mt[i][j]=NULL; ^ main.cpp:54:27: note: within this loop for(int j=0; j<=50; ++j) ~^~~~