Compilare: user.cpp: In function ‘int main(int, const char**)’: user.cpp:23:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( p < str[i - 1].length() && p < str[i].length() && str[i - 1][p] == str[i][p] ) { ^ user.cpp:23:61: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( p < str[i - 1].length() && p < str[i].length() && str[i - 1][p] == str[i][p] ) { ^