Compilare: user.cpp: In function ‘int main()’: user.cpp:96:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i < root[x].size() && i < root[y].size() && root[x][i] == root[y][i]; ++i); --i; ^ user.cpp:96:57: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i < root[x].size() && i < root[y].size() && root[x][i] == root[y][i]; ++i); --i; ^