Compilare: main.cpp: In function 'int main()': main.cpp:17:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<strlen(s);i++) ~^~~~~~~~~~ main.cpp:33:21: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] t[k]=NULL; ^~~~ main.cpp:50:21: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] t[k]=NULL; ^~~~ main.cpp:92:18: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] q[j]=NULL; ^~~~