Compilare: user.cpp: In function ‘int main()’: user.cpp:12:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<strlen(c);++i) ^ user.cpp:18:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=1;j<=strlen(c);++j) ^ user.cpp:31:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=1;i<=strlen(c);++i) ^